SUMMARY

This summary highlights material information in this proxy statement/prospectus. You are urged to carefully read the entire proxy statement/prospectus and the other documents referred to in this proxy statement/prospectus because the information in this section does not provide all of the information that might be important to you with respect to the merger agreement, the merger and other matters being considered at the special meeting. For information on how to obtain the documents that are on file with the Securities and Exchange Commission (the “SEC”), see the section of this proxy statement/prospectus titled “Where You Can Find More Information.” Please see “Certain Defined Terms” and the glossary included as Annex D to this proxy statement/prospectus for the meaning of some of the defined terms used herein.

References in this proxy statement/prospectus to (i) the number of outstanding ETC common shares and the ownership interest of each of the former WMB stockholders and ETE in ETC following the completion of the merger transactions is based on the number of shares of WMB common stock outstanding as of the date of this proxy statement/prospectus and (ii) the ownership interest of ETC in ETE following the completion of the merger transactions is based on the number of shares of WMB common stock and common units representing limited partner interests in ETE (the “ETE common units”) outstanding as of the date of this proxy statement/prospectus.

You are urged to review the information included in the summary section titled “Recent Developments” since the historical information included herein does not fully reflect the impact on ETE or WMB of the significant decline in crude oil and natural gas prices.

The Parties (see page 97)

Energy Transfer Corp LP

Energy Transfer Corp LP is a Delaware limited partnership that will be treated as a corporation for U.S. federal income tax purposes. Upon the completion of the merger transactions (as defined below), ETC’s primary cash generating asset will consist of Class E units, a new class of units representing limited partner interests in ETE (the “ETE Class E units”), which will represent an approximate 57% limited partner interest in ETE following the completion of the merger transactions, excluding any interest attributable to the Series A Convertible Preferred Units in ETE (the “Convertible Units”) issued by ETE in March 2016, as further described in the section titled “Summary—Recent Developments” beginning on page 20 of this proxy statement/prospectus.

ETE has agreed to provide all administrative services to ETC and to indemnify ETC for all non-tax liabilities incurred by ETC. Therefore, ETC expects to distribute 100% of the quarterly cash distributions it receives from ETE in respect of the ETE Class E units, after deducting federal and state income taxes, if any, to the holders of common shares representing limited partner interests in ETC (the “ETC common shares”).

The ETE Class E units will be entitled to receive the same quarterly cash distribution per unit as the quarterly cash distribution paid per ETE common unit. In addition, for any period ending on or before December 31, 2018 (the “dividend equalization period”), ETE is obligated to make distributions and/or special allocations of depreciation or other forms of cost recovery to the ETE Class E units to ensure that ETC has sufficient cash to pay distributions on each ETC common share in an amount equal to 100% of the distributions paid by ETE on each ETE common unit. As discussed in “—Recent Developments—Updated Financial Forecasts of ETC,” following the closing of the merger, ETE does not expect to make any cash distributions with respect to its common units or ETE Class E Units prior to the distribution payable with respect to the quarter ending March 31, 2018. If ETE does not make a cash distribution on its ETE Class E Units until such time, then ETC will not have any cash available for distribution on its common shares.

In general, distributions on ETC common shares will be treated as distributions on corporate stock for federal income tax purposes. No Schedule K-1s will be issued with respect to the ETC common shares, but instead holders of ETC common shares will receive an IRS Form 1099 from ETC or their brokers with respect to the distributions they receive on the ETC common shares.

ETC’s principal executive offices are located at 8111 Westchester Drive, Dallas, Texas 75225, and ETC’s phone number is (214) 981-0700.

Energy Transfer Equity, L.P.

ETE (NYSE: ETE) is a publicly traded master limited partnership whose principal sources of cash flow are derived from its direct and indirect equity interests in Energy Transfer Partners, L.P. (NYSE: ETP), Sunoco Logistics Partners L.P. (NYSE: SXL) and Sunoco LP (NYSE: SUN), all of which are publicly traded master limited partnerships engaged in diversified energy-related businesses. As of March 31, 2016, after giving effect to the Sunoco Retail Acquisition and the Sunoco Equity Offering, ETE’s direct and indirect equity interests in ETP, SXL and Sunoco consisted of the following:

In addition to the equity interests described above, ETE owns all of the equity interests in Lake Charles LNG Company, LLC (“Lake Charles LNG”), an entity that owns a fully constructed liquefied natural gas (“LNG”) import terminal and regasification facility near Lake Charles, Louisiana, and a 60% equity interest in Lake Charles LNG Export, LLC (“LCL”), an entity whose subsidiary is developing an LNG liquefaction and

export terminal facility that will be integrated with Lake Charles LNG’s import/regasification facility. ETP owns the remaining 40% equity interest in LCL.

As of March 31, 2016, the market capitalization of ETE common units totaled approximately $7.45 billion. ETE’s principal executive offices are located at 8111 Westchester Drive, Dallas, Texas 75225, and ETE’s phone number is (214) 981-0700. ETE’s website is located at www.energytransfer.com. Information on ETE’s website or any other website is not incorporated by reference into this proxy statement/prospectus and does not constitute part of this proxy statement/prospectus.

The Williams Companies, Inc.

WMB (NYSE: WMB) is a publicly traded Delaware corporation founded in 1908, originally incorporated under the laws of the state of Nevada in 1949 and reincorporated under the laws of the State of Delaware in 1987. WMB is primarily an energy infrastructure company focused on connecting North America’s hydrocarbon resource plays to growing markets for natural gas, NGLs, and olefins. WMB’s operations span from the deepwater Gulf of Mexico to the Canadian oil sands.

WMB’s interstate gas pipeline and midstream interests are largely held through its significant investment in WPZ, which is a publicly traded energy infrastructure master limited partnership focused on connecting North America’s significant hydrocarbon resource plays to growing markets for natural gas, NGLs and olefins through its gas pipeline and midstream businesses.

The principal executive offices of WMB are located at One Williams Center, Tulsa, Oklahoma 74172-0172, its telephone number is (918) 573-2000, and its website is located at http://co.williams.com. WMB makes available its periodic reports and other information filed with or furnished to the SEC, free of charge, through its website, as soon as reasonably practicable after those reports and other information are electronically filed with or furnished to the SEC. Information on the website or any other website is not incorporated by reference into this proxy statement/prospectus and does not constitute a part of this proxy statement/prospectus.

The Merger (see page 104)

Pursuant to the merger agreement, WMB will merge with and into ETC (the “merger”), with ETC surviving the merger. Immediately thereafter, LE GP will merge with and into ETE GP (the “GP merger” and, together with the merger, the “mergers”), with ETE GP surviving the GP merger and becoming the general partner of ETE.

Immediately following the completion of the mergers, ETC will contribute substantially all of the assets and liabilities it assumed from WMB through the merger to ETE in exchange for the issuance by ETE to ETC of a number of ETE Class E units equal to (i) the number of ETC common shares issued to the WMB stockholders in the merger plus (ii) the number of ETC common shares issued to ETE in consideration for the Parent Cash Deposit (as defined below) (the “WMB Contribution” and, together with the merger and the other transactions contemplated by the merger agreement, the “merger transactions”).

Immediately following the effective time of the mergers, ETC will contribute an amount of cash to ETE GP (the “GP Contribution”), which ETE GP will contribute to ETE in exchange for newly issued ETE common units and general partner units in ETE. As a result of the GP Contribution, the percentage interest in ETE that will be owned by ETE GP after completion of the merger transactions will equal the percentage interest in ETE owned by LE GP immediately prior to the merger transactions.

In connection with the merger, ETE will acquire a number of ETC common shares equal to (i) (a) the share consideration (as defined below) multiplied by (b) the aggregate number of shares of WMB common stock issued and outstanding as of the closing date of the merger (the “closing date”), multiplied by (c) $8.00 (we refer to the product of (b) and (c) as the “cash component”) divided by (ii) the cash consideration (as defined below), in

exchange for the amount of cash needed by ETC to fund the cash portion of the merger consideration (the “Parent Cash Deposit”). As a result, based on the number of shares of WMB common stock outstanding as of the date of this proxy statement/prospectus, ETE will own approximately 19% of the outstanding ETC common shares immediately after the effective time of the merger (the “effective time”) (which percentage becomes approximately 17% after giving effect to the anticipated grant of awards under the Energy Transfer Corp LP 2016 Long-Term Incentive Plan following the merger). For additional information regarding the financing that ETE plans to obtain to fund the Parent Cash Deposit, see the section titled “The Merger—Financing Commitment” on page 193 of this proxy statement/prospectus.

The terms and conditions of the merger are contained in the merger agreement, a composite copy of which, incorporating the amendment into the text of the initial agreement, is attached as Annex A to this proxy statement/prospectus. We encourage you to read the merger agreement carefully and in its entirety, as it is the legal document that governs the merger.

Merger Consideration (see page 197)

Upon completion of the merger, each issued and outstanding share of WMB common stock (other than shares of WMB common stock held by WMB, subsidiaries of WMB, ETC and its affiliates and shares for which the holder thereof has properly demanded appraisal under Delaware law (and who does not fail to perfect or otherwise effectively withdraw their demand or waive or lose the right to appraisal, which shares we refer to as “appraisal shares”)) will be converted into the right to receive, at the election of each WMB stockholder, but subject to the election and proration procedures described below:

In addition, each ETC common share issued in the merger will have attached to it one contingent consideration right (a “CCR”).

WMB stockholders that elect to receive the share consideration or the cash consideration will be subject to proration to ensure that the aggregate number of ETC common shares and the aggregate amount of cash paid in the merger will be the same as if all electing shares received the mixed consideration.

WMB stockholders receiving consideration in ETC common shares will not receive any fractional ETC common shares in the merger. Instead, WMB stockholders will receive cash (payable in U.S. dollars, without interest) in lieu of any fractional ETC common shares that they would otherwise have been entitled to receive.

For more information, please see the sections titled “The Merger Agreement—Merger Consideration” and “CCR Agreement” beginning on pages 197 and 217, respectively, of this proxy statement/prospectus.

Appraisal Rights (see page 254)

Under Section 262 of the General Corporation Law of the State of Delaware (the “DGCL”), WMB stockholders will be entitled to appraisal rights in connection with the merger. To perfect appraisal rights, a WMB stockholder, among other things, must not vote for the adoption of the merger agreement, must continue to hold his, her or its shares of WMB common stock through the effective time and must comply with all the procedures required under Delaware law, including delivering a written demand for appraisal to WMB before the taking of the vote on the adoption of the merger agreement. Failure to follow any of the statutory procedures set forth in Section 262 will result in the loss of appraisal rights under Delaware law. Because of the complexity of Delaware law relating to appraisal rights, if any WMB stockholder is considering exercising his, her or its appraisal rights, ETC and WMB encourage such WMB stockholder to seek the advice of his, her or its own legal counsel.

A summary of the requirements under Delaware law to exercise appraisal rights is included in this proxy statement/prospectus in the section titled “Appraisal Rights” beginning on page 254, and the text of Section 262 of the DGCL as in effect with respect to the merger is attached as Annex E to this proxy statement/prospectus.

Accounting Treatment of the Merger (see page 190)

In accordance with accounting principles generally accepted in the United States and in accordance with the Financial Accounting Standards Board’s Accounting Standards Codification Topic 805—Business Combinations, ETC will account for the merger as an acquisition of a business.

Treatment of WMB Equity Awards (see page 201)

At the effective time, ETC will assume all obligations of WMB under the WMB stock plans with respect to outstanding awards issued thereunder. The number and kind of shares available for issuance under the WMB stock plans assumed by ETC will be converted and adjusted to reflect the fact that converted awards will correspond to ETC common shares, although all converted awards will be settled in cash.

WMB Stock Options. Each WMB stock option will be equitably adjusted immediately prior to the effective time by reducing the exercise price thereof by an amount equal to the pre-merger special dividend, contingent on the consummation of the merger.

At the effective time, each unexercised WMB stock option will be assumed by ETC and converted into a cash-settled stock appreciation right, on otherwise the same terms and conditions as were applicable under the corresponding WMB stock option, adjusted in a manner intended to preserve the aggregate intrinsic value of the original WMB stock option. In order to preserve the intrinsic value, the ETC cash-settled stock appreciation right will correspond to a number of ETC common shares (determined by multiplying the number of shares of WMB common stock subject to the WMB stock option by an exchange ratio (as defined below) and rounding down to the nearest whole share), at a base price per share (rounded up to the nearest whole cent) determined by dividing the per-share exercise price of the WMB stock option by that same exchange ratio. For purposes of adjusting the WMB stock options, the exchange ratio is equal to the ratio of the average of the volume-weighted average prices of WMB common stock over the 10 trading days preceding the closing date to the average of the volume-weighted average prices of ETC common shares over the 10 trading days following the closing date.

WMB Restricted Stock Units and WMB Deferred Stock Units. At the effective time, each WMB restricted stock unit (including WMB performance stock units) and each WMB deferred stock unit will be assumed by ETC and converted into a cash-settled restricted stock unit or deferred stock unit, as applicable, on otherwise the same terms and conditions as were applicable under the corresponding WMB restricted stock unit or WMB deferred stock unit, as applicable, with the number of ETC common shares covered by the award adjusted based on the share consideration ratio, rounded down to the nearest whole share. In addition, with respect to each WMB performance stock unit, performance conditions will generally be deemed to be satisfied at target (in the case of WMB performance stock units) or the greater of target and actual performance (in the case of WMB leveraged performance stock units) and, following the effective time, the vesting of the award will be time-based and subject to continued employment through the end of the applicable performance period or any other date required by the terms of the applicable award. Holders of converted WMB restricted stock units and WMB deferred stock units will also be entitled to receive upon settlement of the unit (1) the pre-merger special dividend and payment of any other accrued dividend equivalents, (2) a cash payment in respect of any fractional ETC common shares that would have resulted from such conversion without regard to rounding and (3) if such unit settles after the end of the CCR measurement period, an amount in cash equal to the shortfall amount (if any). The value of any payments in respect of fractional ETC common shares will be based on the same value of ETC common shares used for purposes of converting WMB stock options.

The Special Meeting; Required Vote (see page 100)

The special meeting of WMB stockholders (the “special meeting”) will be held on June 27, 2016 at 9:00 a.m., local time, at The Williams Resource Center Theater, One Williams Center, Tulsa, Oklahoma 74172. At the special meeting, you will be asked to consider and vote on the following proposals:

Approval of the Merger Proposal requires the affirmative vote of holders of a majority of the outstanding shares of WMB common stock.

The affirmative vote of a majority of the votes cast affirmatively or negatively on the Compensatory Proposal is required to approve, on an advisory basis, the Compensatory Proposal, but this vote will not be binding on WMB, the Board of Directors of WMB (the “WMB Board”) or any of its committees.

The approval of the Adjournment Proposal requires the affirmative vote of a majority of the votes cast on such proposal at the special meeting, regardless of whether a quorum is present.

Corvex Management LP (“Corvex”) and Soroban Master Fund LP (“Soroban”), as of the close of business on February 26, 2016, held, directly or indirectly, and therefore controlled the power to vote or direct the voting of, 8.38% of the combined voting power of WMB common stock. Under the terms of the Settlement Agreement, dated as of February 25, 2014, by and among Corvex, Keith Meister, Soroban, Soroban Capital Partners LLC, Eric W. Mandelblatt and WMB, because Keith Meister and Eric W. Mandelblatt, in their capacity as WMB directors voted in favor of the Merger Proposal at a meeting of the WMB Board, Corvex and Soroban are required to cause their shares of WMB common stock to be voted in accordance with the WMB Board’s recommendation with respect to such matter. As a result, due to the WMB Board’s recommendation “for” the Merger Proposal, 8.38% of the combined voting power of WMB common stock will be voted in favor of the Merger Proposal.

Recommendation of the WMB Board and Its Reasons for the Merger (see page 132)

After careful consideration, on September 28, 2015, a majority of the WMB Board (a) approved and declared advisable and resolved to recommend to its stockholders the adoption of the merger agreement, the merger and the other merger transactions and (b) declared that it is in the best interests of the WMB stockholders for WMB to enter into the merger agreement and consummate the merger and the other merger transactions. Since such time, the WMB Board has, among other things, carefully reviewed the developments described in “Summary—Recent Developments” beginning on page 20 of this proxy statement/prospectus. As of the date of this proxy statement/prospectus, a majority of the WMB Board continue to recommend a vote “FOR” the Merger Proposal. Certain members of the WMB Board voted on September 28, 2015 against entering into the merger agreement and continue as of the date of this proxy statement/prospectus to disagree with the recommendation of a majority of the WMB Board that WMB stockholders adopt the merger agreement. See section titled “The Merger—Background of the Merger” beginning on page 104 of this proxy statement/prospectus. A majority of the WMB Board also recommend a vote “FOR” the non-binding Compensatory Proposal, and the WMB Board unanimously recommend a vote “FOR” the approval of the Adjournment Proposal, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the special meeting to approve the Merger Proposal.

For a discussion of the material factors that the WMB Board considered in determining to approve the Merger Proposal, see the section titled “The Merger—Recommendation of the WMB Board and Its Reasons for the Merger” beginning on page 132 of this proxy statement/prospectus.

WMB’s reasons for the transaction are forward-looking in nature and, therefore, should be read in light of the risk factors discussed in the sections of this proxy statement/prospectus titled “Risk Factors” and “Forward-Looking Statements, as well as the forward-looking information, including the prospective financial information, in the section titled “Summary—Recent Developments” beginning on page 20 of this proxy statement/prospectus.

Opinions of the Financial Advisors to the WMB Board (see page 143)

At a meeting of the WMB Board held on September 28, 2015, each of Barclays Capital Inc. (“Barclays”) and Lazard Freres & Co. (“Lazard”) delivered the fairness opinions further described below. The WMB Board acknowledges that the fairness opinions of Barclays and Lazard only address fairness of the consideration to be received by WMB stockholders as of September 28, 2015 and the WMB Board no longer believes that the projections underlying the fairness opinions are valid. Accordingly, the WMB Board is not relying on the fairness opinions of Barclays and Lazard in evaluating its recommendation to WMB stockholders to adopt the merger agreement in light of the developments described in “Summary—Recent Developments” beginning on page 20 of this proxy statement/prospectus.

Opinion of Barclays Capital Inc. (see page 143)

At a meeting of the WMB Board held on September 28, 2015, Barclays delivered an oral opinion to the WMB Board, which was subsequently confirmed in writing, to the effect that, as of such date and based upon and subject to the qualifications, limitations and assumptions stated therein, the merger consideration to be paid in the aggregate to the WMB stockholders is fair, from a financial point of view, to such stockholders.

The terms of the merger were determined through arm’s-length negotiations between WMB, on the one hand, and ETE, on the other hand, and were approved on September 28, 2015 by a majority vote of the WMB Board. Barclays did not recommend any specific form or amount of consideration to WMB or that any specific form or amount of consideration constituted the only appropriate consideration for the merger. Barclays was not requested to address, and its opinion does not in any manner address, WMB’s underlying business decision to proceed with or effect the merger or the likelihood of consummation of the merger or the relative merits of the merger as compared to any strategic alternatives that may be available to WMB. In addition, Barclays expressed no opinion on, and its opinion does not in any manner address, the fairness of the amount or the nature of any compensation to any officers, directors or employees of any parties to the merger, or any class of such persons, relative to the merger consideration to be paid in the aggregate by ETC in the merger or otherwise. No limitations were imposed by the WMB Board upon Barclays with respect to the investigations made or procedures followed by it in rendering its opinion. The full text of Barclays’ written opinion, dated as of September 28, 2015, is attached hereto as Annex F. Barclays’ written opinion sets forth, among other things, the assumptions made, procedures followed, factors considered and limitations upon the review undertaken by Barclays in rendering its opinion. You are encouraged to read the opinion carefully in its entirety. This summary is qualified in its entirety by reference to the full text of the opinion. See “The Merger—Opinions of the Financial Advisors to the WMB Board—Opinion of Barclays.”

Opinion of Lazard Frères & Co. (see page 155)

At a meeting of the WMB Board held on September 28, 2015, Lazard delivered an oral opinion to the WMB Board, which was subsequently confirmed in writing, to the effect that, as of such date and based upon and subject to the assumptions, procedures, factors, qualifications and limitations stated therein, the merger

consideration to be paid to WMB stockholders (other than certain WMB stockholders excluded from the scope of Lazard’s opinion as set forth in Lazard’s written opinion) in the merger was fair, from a financial point of view, to such WMB stockholders.

The terms of the merger were determined through arm’s-length negotiations between WMB, on the one hand, and ETE, on the other hand, and were approved on September 28, 2015 by a majority vote of the WMB Board. Lazard’s opinion was directed to the WMB Board (in its capacity as such) in connection with the WMB Board’s evaluation of the merger and only addressed the fairness, from a financial point of view, to WMB stockholders (other than certain WMB stockholders excluded from the scope of Lazard’s opinion as set forth in Lazard’s written opinion) of the merger consideration to be paid to such WMB stockholders in the merger. Lazard’s opinion was not intended to and does not constitute a recommendation to any WMB stockholder as to how such stockholder or other person should vote or act with respect to the merger or any matter relating thereto. Lazard did not express any opinion as to the prices at which shares of WMB common stock, the ETC common shares (including the attached CCRs), the ETE common units or the ETE Class E units may trade at any time subsequent to the announcement of the merger. Lazard did not express any opinion as to any tax or other consequences that might result from the merger or related transactions contemplated by the merger agreement, nor did its opinion address any legal, tax, regulatory or accounting matters, as to which Lazard understood that WMB obtained such advice as it deemed necessary from qualified professionals. In addition, Lazard’s opinion did not address the relative merits of the merger as compared to any other transaction or business strategy in which WMB might engage or the merits of the underlying decision by WMB to engage in the merger and related transactions contemplated by the merger agreement. In addition, Lazard expressed no view or opinion as to any terms or other aspects (other than the merger consideration to the extent expressly specified in Lazard’s written opinion) of the merger and related transactions contemplated by the merger agreement, including, without limitation, the form or structure of the merger or any agreements or arrangements entered into in connection with, or contemplated by, the merger or the related transactions contemplated by the merger agreement. The summary of Lazard’s opinion set forth herein is qualified in its entirety by reference to the full text of Lazard’s opinion, which is attached hereto as Annex G, and which you are encouraged to carefully read in its entirety.

Reasons of ETE General Partner’s Board for the Merger (see page 174)

At a meeting held on September 27, 2015, after due consideration and consultation with ETE’s management and its legal and financial advisors, the board of directors of ETE’s general partner, LE GP, unanimously approved the merger agreement and the transactions contemplated thereby, including the merger, the GP merger and the WMB Contribution. In reaching its determination to approve the merger agreement, the board of directors of LE GP considered a number of factors based on facts and circumstances that existed as of September 27, 2015, including:

ETE’s reasons for the transaction are forward-looking in nature and, therefore, should be read in light of the factors discussed in the sections of this proxy statement/prospectus titled “Risk Factors” and “Forward-Looking Statements” and in this Summary section titled “Recent Developments” beginning on page 20 of this proxy statement/prospectus, which section includes a description of certain facts and circumstances arising after September 27, 2015 and the effect that those facts and circumstances have had on certain factors considered by the board of directors of LE GP at the time of approving the merger, as well as certain prospective financial information for ETC that takes into account the facts and circumstances set forth in such section. The reasons of the board of directors of LE GP as of September 27, 2015 for approving the merger do not take into account the facts and circumstances described in the section titled “Summary—Recent Developments,” including the prospective financial information set forth therein, should not be relied upon as reflective of the current views of the board of directors of LE GP and do not constitute a recommendation by the board of directors of LE GP as to how WMB stockholders should vote with respect to the Merger Proposal. The adverse impact of the decline in crude oil and natural gas prices together with the refinancing risks related to the $6.05 billion in new indebtedness expected to be incurred by ETE in connection with the merger, significantly reduces the value of ETC as compared to the value envisioned by the board of directors of LE GP at the time the merger agreement was entered into.

No ETE Unitholder Approval (see page 190)

Approval of ETE unitholders is not required to adopt the merger agreement or approve the merger or the issuance of the ETC common shares or ETE Class E units in connection with the merger transactions.

Financing Commitment (see page 193)

On October 21, 2015, ETE entered into an Amended and Restated Commitment Letter (the “Commitment Letter”) with a syndicate of 20 banks (collectively, the “Commitment Parties”). Pursuant to the Commitment Letter, the Commitment Parties have committed to provide a 364-day secured term loan credit facility in an aggregate principal amount of $6.05 billion (or such lesser amount that ETE may elect to borrow). The total interest rate on such facility is capped at 5.50%, and the facility can be extended for an additional one year at the election of ETE. The commitment is subject to customary conditions for commitments of this type, including the execution of satisfactory definitive documentation.

Board of Directors of the General Partner of ETC After the Merger (see page 344)

Upon completion of the merger, the board of directors of the general partner of ETC (the “ETC GP Board”) will consist of between five and 11 directors, including at least three independent directors meeting the independence standards established by the NYSE and the Exchange Act. The directors will all be designated and elected by the Existing GP Owner, but the independent directors who will serve on the conflicts committee of the ETC GP Board must also be approved by the WMB Board, with such approval not to be unreasonably withheld. The Existing GP Owner has selected John W. McReynolds, Thomas E. Long, Marshall S. McCrea, III, Thomas P. Mason, James W. Bryant, Imad K. Anbouba and M. Max Yzaguirre as, and such individuals have agreed to serve as, directors of the ETC GP Board, effective in connection with the closing of the merger. The Existing GP Owner has proposed James W. Bryant, Imad K. Anbouba and M. Max Yzaguirre as its nominees for the conflicts committee of the ETC GP Board. On May 18, 2016, the WMB Board approved these nominees.

Interests of Directors and Executive Officers of WMB in the Merger (see page 176)

In considering the recommendation of a majority of the WMB Board to approve the merger, WMB stockholders should be aware that certain WMB directors and executive officers may be deemed to have interests in the merger that are in addition to, or different from, the interests of other WMB stockholders. The WMB Board was aware of these interests and considered them, among other matters, in approving the merger and the merger agreement and in making the recommendations that the WMB stockholders approve the merger agreement, the merger and the other merger transactions. These interests include:

Risk Factors Relating to the Merger and Ownership of ETC Common Shares (see pages 45 and 55)

You should consider all the information contained in or incorporated by reference into this proxy statement/prospectus in deciding how to vote for the proposals presented in this proxy statement/prospectus. In particular, you should consider the risks relating to the merger described in the section titled “Risks Related to the Merger” beginning on page 45 of this proxy statement/prospectus, some of which are summarized below:

There are also several risks related to the CCRs and the Contingent Consideration Rights Agreement (the “CCR agreement”), which you should consider:

You should also consider the risks relating to the ownership of ETC common shares described in the section titled “Risks Related to ETC and the Ownership of ETC Common Shares” beginning on page 55 of this proxy statement/prospectus, some of which are summarized below:

Material U.S. Federal Income Tax Consequences of the Merger (see page 230)

It is a condition to WMB’s obligation to complete the merger that WMB receive a written opinion from Cravath, Swaine & Moore LLP (“Cravath”), special counsel to WMB, to the effect that the merger will qualify as a “reorganization” within the meaning of Section 368(a) of the Code. It is a condition to ETC’s obligation to complete the merger that ETC receive a written opinion from Latham to the effect that the merger will qualify as a “reorganization” within the meaning of Section 368(a) of the Code. In addition, in connection with the filing of the registration statement of which this document is a part, each of Cravath and Latham has delivered an opinion to WMB and ETC, respectively, to the same effect.

The parties intend to treat the merger as a “reorganization” within the meaning of Section 368(a)(1)(F) of the Code. Accordingly, U.S. holders of WMB common stock generally will not recognize gain or loss for U.S. federal income tax purposes upon their receipt of ETC common shares in exchange for WMB common stock pursuant to the merger. However, (a) U.S. holders of WMB common stock that receive cash pursuant to the merger generally will recognize gain or loss equal to the difference between the amount of any cash received and the holder’s adjusted tax basis in the shares of WMB common stock surrendered for such cash consideration (as designated by the holder); (b) U.S. holders of WMB common stock that receive cash in connection with the settlement of a CCR will be treated as receiving a distribution with respect to their ETC common shares taxable as a dividend to the extent of such holder’s ratable share of ETC’s current and accumulated earnings and profits; and (c) U.S. holders of WMB common stock generally will recognize gain or loss with respect to cash received in lieu of fractional ETC common shares that such holders would otherwise be entitled to receive.

It is possible, however, that the IRS will treat the merger as a “reorganization” within the meaning of Section 368(a)(1)(A) of the Code (instead of Section 368(a)(1)(F) of the Code). In such a case, U.S. holders would still not recognize gain or loss upon their receipt of ETC common shares in exchange for WMB common stock but would be subject to different tax treatment with respect to any cash received pursuant to the merger and in connection with the cash settlement of a CCR, as described under the headings “Material U.S. Federal Income Tax Consequences of the Merger—Possible Treatment of Merger as a Reorganization Pursuant to Section 368(a)(1)(A) of the Code—Exchange for ETC Common Shares and Cash” and “Material U.S. Federal Income Tax Consequences of the Merger—Possible Treatment of Merger as a Reorganization Pursuant to Section 368(a)(1)(A) of the Code—Contingent Consideration Rights.”

For further information, please refer to the discussion under the heading “Material U.S. Federal Income Tax Consequences of the Merger.” Holders of WMB common stock should consult their own tax advisors to determine the particular tax consequences to them of the merger (including the application and effect of any state, local or non-U.S. income and other tax laws).

Certain U.S. Federal Income Tax Considerations of the WMB Contribution (see page 237)

Immediately following the completion of the merger, pursuant to the contribution agreement, ETC will contribute substantially all of the assets and liabilities it assumed from WMB through the merger to ETE in exchange for the issuance by ETE to ETC of a number of ETE Class E units equal to (i) the number of ETC common shares issued to the WMB stockholders in the merger plus (ii) the number of ETC common shares issued to ETE in exchange for the amount of cash needed by ETC to fund the cash portion of the merger consideration. Completion of the merger is subject to satisfaction or waiver of a number of conditions, including

the receipt by ETC and WMB of the 721 Opinion from Latham. Latham has advised ETE that, considering the potential claims that the IRS may successfully assert and the level of uncertainty regarding the ultimate outcome of these claims, Latham would not be able to deliver the 721 Opinion were the opinion requested as of the date of this proxy statement/prospectus.

ETE believes that if the WMB Contribution is not an exchange to which Section 721(a) of the Code applies, ETC would likely be required to pay a material amount of tax as a result of the transaction. Under the terms of the contribution agreement, ETE will indemnify ETC pursuant to the contribution agreement for any taxes incurred by ETC as a result of the merger transactions, including the WMB Contribution. However, since ETC’s primary cash generating asset following the merger will consist of ETE Class E units, any material adverse impact on ETE from such indemnification will have a material adverse impact on ETC. As a consequence, it is unlikely that ETC would waive the condition to closing that ETC receive the 721 Opinion from Latham.

Cravath disagrees with Latham’s position and has advised WMB that it is willing to deliver an opinion that the WMB Contribution should qualify as an exchange to which 721(a) of the Code applies. Based on the information available to WMB as of the date of this proxy statement/prospectus, WMB believes that the WMB Contribution should qualify as an exchange to which Section 721(a) of the Code applies. WMB is, therefore, willing to waive the condition to closing that WMB receive the 721 Opinion from Latham. In addition, on May 13, 2016, WMB filed a lawsuit against ETE in the Delaware Court of Chancery seeking, among other remedies, a declaratory judgment and injunction preventing ETE from terminating or otherwise avoiding its obligations under the merger agreement due to any failure of Latham to deliver the 721 Opinion to ETC and WMB. ETE believes that the allegations underlying the lawsuit are without merit and intends to vigorously defend against them. Please see “Recent Developments—Litigation Related to the 721 Opinion and the Outside Date.”

Listing of the ETC Common Shares; Delisting and Deregistration of Shares of WMB Common Stock (see page 193)

It is a condition to the completion of the merger that the ETC common shares and attached CCRs to be issued to WMB stockholders and ETE in connection with the merger transactions be approved for listing on the NYSE, subject to official notice of issuance. We intend to apply for listing on the NYSE under the symbol “ETC”. When the merger is completed, the WMB common stock currently listed on the NYSE will be delisted from the NYSE and deregistered under the Exchange Act.

Conditions to Completion of the Merger (see page 210)

The obligations of each of ETE and WMB to effect the merger are subject to the satisfaction or waiver of the following conditions:

We cannot be certain when, or if, the conditions to the merger will be satisfied or waived, or that the merger will be completed.

The obligations of ETC and ETE to effect the merger are also subject to the satisfaction or waiver of the following conditions:

The obligation of WMB to effect the merger is also subject to the satisfaction or waiver of the following conditions:

Regulatory Approvals (see page 190)

To complete the merger, ETE and WMB must obtain approvals or consents from, or make filings with, certain U.S. federal and international authorities. The material regulatory approvals, consents and filings include the following:

The merger agreement provides that ETE and WMB will make the necessary filings and submissions for the above-mentioned authorizations and approvals and will use their reasonable best efforts to obtain these authorizations and approvals. In addition, WMB and ETE are required to obtain certain state or local approvals in connection with the merger. Although ETE and WMB believe that they will receive the required authorizations and approvals described above to complete the merger, we cannot give any assurance as to the timing of these consents and approvals or as to ETE’s or WMB’s ultimate ability to obtain such consents or approvals (or any additional consents or approvals that may otherwise become necessary). We also cannot ensure that we will obtain such authorizations or approvals on terms and subject to conditions satisfactory to ETE and WMB.

No Solicitation by WMB of Alternate Proposals (see page 206)

As more fully described in this proxy statement/prospectus and in the merger agreement, and subject to certain exceptions summarized below, WMB has agreed not to solicit, initiate, knowingly encourage, or knowingly facilitate inquiries or proposals with respect to, or engage or participate in any negotiations concerning, or provide any confidential or nonpublic information to any person relating to, an alternative takeover proposal. Notwithstanding these restrictions, the merger agreement provides that WMB may participate in discussions or negotiations or furnish nonpublic information regarding WMB in response to an unsolicited bona fide written takeover proposal, and under specific circumstances, including the WMB Board’s determination (in accordance with the merger agreement and after consultation with WMB’s outside legal counsel and financial advisors) that the failure to take such actions would be more likely than not to result in a violation of its fiduciary duties under applicable law, and that the terms of such transaction would be more favorable to WMB stockholders than the merger.

Change in WMB Board Recommendation (see page 207)

The WMB Board may effect an adverse recommendation change in response to an intervening event, or enter into an alternative acquisition agreement in response to an unsolicited superior proposal, without breaching its no-solicitation obligations under the merger agreement. The WMB Board’s ability to do so is subject to certain other requirements, including the provision of written notice to ETE, the good faith negotiation with ETE to revise the terms of the merger agreement, and, where the adverse recommendation change is in response to an intervening event, the good faith determination that the WMB Board would breach its fiduciary duties under applicable law if it failed to make such recommendation.

Termination of the Merger Agreement (see page 213)

WMB and ETE may mutually agree to terminate the merger agreement and abandon the merger at any time before the consummation of the merger. Subject to conditions and circumstances described in the merger agreement, the merger agreement may be terminated as follows:

Expenses (see page 214)

If the merger agreement is terminated by ETE or ETC following the failure of WMB stockholders to approve the merger proposal at the special meeting, then WMB will reimburse ETE for all out-of-pocket fees and expenses incurred in connection with the merger, up to $50.0 million. If the merger agreement is terminated by ETE or WMB due to the breach by the other party of its representations, warranties, covenants or agreements set forth in the merger agreement, then the breaching party will reimburse all out-of-pocket fees and expenses incurred by the other party in connection with the merger, up to $100.0 million.

Termination Fee (see page 214)

WMB will be required to pay ETE a termination fee of $1.48 billion if:

ETE will also be required to reimburse WMB $410.0 million for a portion of the termination fee paid by WMB to terminate its previous merger agreement with WPZ if certain conditions to WMB’s obligation to consummate the merger have not been satisfied and the merger agreement is terminated by ETE or WMB due to: (i) a permanent injunction or final, non-appealable governmental order or action being in effect; (ii) ETE or ETC’s breach of any of its representations, warranties, covenants, or agreements set forth in the merger agreement; or (iii) the failure to consummate the merger within the outside date. Any expenses of ETE reimbursed by WMB are creditable against the termination fee.

Comparison of Rights of ETC Shareholders and WMB Stockholders (see page 240)

The rights of WMB stockholders are currently governed by WMB’s amended and restated certificate of incorporation and by-laws and by the DGCL. WMB stockholders who receive the merger consideration in ETC common shares will become shareholders of ETC upon completion of the merger. Thereafter, their rights will be governed by ETC’s certificate of limited partnership, ETC’s partnership agreement and the Delaware Revised Uniform Limited Partnership Act. As a result, these WMB stockholders will have different rights once they become shareholders of ETC due to the differences in the governing documents of and laws applicable to ETC and WMB. The key differences are described in the section titled “Comparison of Rights of ETC Shareholders and WMB Stockholders.”

Amendment of ETE Partnership Agreement (see page 193)

In conjunction with the GP merger, ETE GP will enter into the ETE partnership agreement amendment providing for the creation and issuance of the ETE Class E units with the rights, privileges and obligations set forth in the partnership agreement amendment.

Litigation Relating to the Merger (see page 193)

Between October 5, 2015, and December 24, 2015, purported WMB stockholders filed six putative class action lawsuits in the Delaware Court of Chancery challenging the merger. The suits are captioned Greenwald et al. v. The Williams Companies, Inc., et al., C.A. No. 11573-VCG; Ozaki v. Armstrong et al., C.A. No. 11574-VCG; Blystone v. The Williams Companies, Inc., et al., C.A. No. 11601-VCG; Glener et al. v. The Williams Companies, Inc., et al., C.A. No. 11606-VCG; Amaitis et al. v. Armstrong et al., C.A. No. 11809-VCG; and State-Boston Retirement System et al. v. Armstrong et al., C.A. No. 11844-VCG. The complaints assert various claims against the individual members of the WMB Board; ETE, ETC, ETC GP, LE GP and ETE GP (the “ETE Defendants”); WMB; Barclays; and Lazard. The Ozaki and Blystone complaints allege that the individual members of the WMB Board have breached their fiduciary duties to WMB stockholders by agreeing to sell WMB through an allegedly unfair process and for an allegedly unfair price, and that the ETE Defendants have aided and abetted this purported breach of fiduciary duties. The Greenwald and Glener complaints make similar allegations, but also claim that WMB has aided and abetted the individual members of the WMB Board’s purported breach of fiduciary duties. The Amaitis and State-Boston Retirement System complaints allege that the individual members of the WMB Board who voted for the merger have breached their fiduciary duties to WMB stockholders by agreeing to sell WMB through an allegedly unfair process and for an allegedly unfair price, and that all the individual members of the WMB Board have violated their fiduciary duties by allegedly failing to disclose material information about the merger. The Amaitis complaint additionally alleges that the ETE Defendants, Barclays and Lazard have aided and abetted the individual members of the WMB Board’s supposed breach of fiduciary duties. All the complaints seek, among other things, an injunction against the merger and an

award of costs and attorneys’ fees. On January 13, 2016, the Court consolidated, pursuant to a stipulation among the plaintiffs, these six actions into a new consolidated action captioned In re The Williams Companies, Inc. Merger Litigation, Consolidated C.A. No. 11844-VCG (the “Merger Litigation”). In its stipulated order, the Court designated the complaint from the State-Boston action as operative, and it dismissed without prejudice the ETE Defendants, Barclays and Lazard from the consolidated action. On January 19, 2016, the defendants in the Merger Litigation moved to dismiss the operative complaint. On March 22, 2016, the Court stayed briefing and discovery in the Merger Litigation until the merger between ETE and WMB is consummated and plaintiffs in the Merger Litigation have filed an amended complaint.

On December 4, 2015, a purported WMB stockholder filed an amended complaint in a putative class action lawsuit pending in the Delaware Court of Chancery captioned In re The Williams Companies, Inc. Stockholder Litigation, Consol. C.A. No. 11236-VCG (the “Stockholder Litigation”). The complaint asserts claims against all of the individual members of the WMB Board other than Mr. Meister and Mr. Mandelblatt. The complaint alleges that WMB’s preliminary proxy statement is false and misleading. As relief, the complaint requests, among other things, an injunction requiring WMB to make supplemental disclosures and an award of costs and attorneys’ fees. On December 9, 2015, the defendants in the Stockholder Litigation moved to dismiss the amended complaint. On March 7, 2016, the Court dismissed the amended complaint in a ruling from the bench.

On January 14, 2016, a purported WMB stockholder filed a putative class action lawsuit against WMB and ETE, captioned Bumgarner v. The Williams Companies, Inc., et al., Case No. 16-cv-26-GKF-FHM, in the United States District Court for the Northern District of Oklahoma. The plaintiff alleges that ETE and WMB have violated Section 14 of the Exchange Act by making allegedly false statements concerning the merger. As relief, the complaint seeks an injunction against the proposed merger. On February 1, 2016, the plaintiff filed an amended complaint, making substantially the same allegations. On February 19, 2016, the defendants in the Bumgarner action moved to dismiss the amended complaint. On April 21, 2016, the plaintiff moved for expedited proceedings and expedited discovery. On April 25, 2016, the defendants filed a response in opposition to the plaintiff’s motion for expedition, and also filed a second motion to dismiss. On April 28, 2016, the court denied the defendants’ second motion to dismiss, but granted the original motion to dismiss the amended complaint. The court denied expedited discovery, but granted expedited proceedings and also granted the plaintiff permission to amend his complaint. On May 12, 2016, the plaintiff filed his second amended complaint in the Bumgarner action. The plaintiff alleges that ETE and WMB have violated the Exchange Act by making allegedly false statements concerning the merger and failing to disclose material information concerning, among other topics, (a) the reasons for the changes in the estimated commercial synergies, (b) WMB Board members’ potential conflicts of interest and (c) how the WMB Board ascertained that the directors who voted against the transaction subsequently determined to support the WMB Board’s commitment to consummate the transaction as required by the terms of the merger agreement, including such directors’ current beliefs.

On January 15, 2016, a purported WMB stockholder filed a putative class action lawsuit in the Delaware Court of Chancery against the individual members of the WMB Board, captioned Ryan v. Armstrong et al., C.A. No. 11903-VCG. The complaint asserts that all of the individual members of the WMB Board breached their fiduciary duties in agreeing to the WPZ merger and that a majority of the individual members of the WMB Board breached their fiduciary duties by failing to negotiate for a “collar” provision in connection with the merger with ETE. As relief, the complaint seeks, among other things, damages and an award of costs and attorneys’ fees. On February 22, 2016, the defendants moved to dismiss the complaint, and on March 24, 2016, the defendants filed a brief in support of their motion to dismiss. On April 22, 2016, the plaintiff filed an amended complaint.

On January 19, 2016, a purported WMB stockholder filed a putative class action lawsuit against WMB, the individual members of the WMB Board and the ETE Defendants, captioned City of Birmingham Retirement and Relief System v. Armstrong et al., Case No. 1:16-cv-00017-RGA, in the United States District Court for the District of Delaware. The lawsuit alleges that the individual members of the WMB Board have violated their duty of

disclosure by issuing a supposedly misleading proxy statement in support of the transaction, that a majority of the individual members of the WMB Board violated their fiduciary duties by voting in favor of the merger and that the ETE Defendants aided and abetted this supposed breach of fiduciary duties. The complaint also alleges that the individual members of the WMB Board and WMB have violated Section 14 of the Exchange Act by issuing a supposedly misleading proxy statement and that all defendants have violated Section 20 of the Exchange Act by supposedly causing a misleading proxy statement to be issued. As relief, the complaint seeks, among other things, injunctive relief, damages and an award of costs and attorneys’ fees. On February 10, 2016, WMB and the individual members of the WMB Board moved to dismiss the complaint. On February 18, 2016, the ETE Defendants moved to dismiss the complaint. On March 7, 2016, the plaintiff voluntarily dismissed its complaint.

The defendants believe the allegations in the various complaints noted above are without merit.

The CCR Agreement (see page 217)

The rights of ETC shareholders with respect to the CCRs attached to the ETC common shares will be governed by and subject to the terms and conditions of the CCR agreement, which is attached as Annex B to this proxy statement/prospectus and is incorporated by reference into this proxy statement/prospectus.

The CCR agreement entitles each CCR holder to receive ETC common shares or a cash payment, at ETE’s election, should the average of the daily volume-weighted average price for ETE common units on the NYSE (“ETE common units VWAP”) be greater than the average of the daily volume-weighted average price for ETC common shares on the NYSE (“ETC common shares VWAP”) for a period of 23 months following the 20th trading day after the closing date (the “measurement period”). If the ETC common shares VWAP is less than the ETE common units VWAP for the measurement period (such difference, a “shortfall amount”), then each outstanding CCR will be automatically cancelled and converted into the right to receive a shortfall payment. The shortfall payment will be, at ETE’s election, either:

Notwithstanding the above, the aggregate cash payment cannot exceed an amount of cash equal to (a) 55% of the value of the merger consideration minus (b) the sum of (i) the pre-merger special dividend, (ii) the cash component of the merger consideration, (iii) the aggregate amount of cash paid to former holders of WMB common stock in lieu of issuing fractional ETC common shares and (iv) the aggregate amount of cash paid in respect of appraisal shares. If the aggregate cash payment exceeds this sum, then any difference will be paid in ETC common shares valued at the settlement calculation VWAP.

If, however, the ETC common shares VWAP is equal to or greater than the ETE common units VWAP for the measurement period, then each outstanding CCR will be immediately and automatically cancelled and no consideration of any kind will be delivered to CCR holders in respect of the CCRs. Furthermore, ETE will cancel as an adjustment to the number of ETE Class E units issued to ETC in the WMB Contribution, a number of ETE Class E units equal to (a) (i) the number of outstanding CCRs multiplied by (ii) a fraction, the numerator of which is the excess amount and the denominator of which is the settlement calculation VWAP, multiplied by (b) the ratio of ETE Class E units held by ETC and its subsidiaries over the number of ETC common shares outstanding. See the section titled “The Merger” beginning on page 104 of this proxy statement/prospectus.

The CCRs will be automatically cancelled and extinguished, without consideration of any kind being delivered to CCR holders in respect of the CCRs, and ETE, ETC and the rights agent will have no further obligations with respect to the CCRs, in the event that both of the following exist at any time during the period between the start date and the end date:

There are numerous risks associated with the CCRs, including the possibility that CCR holders will not receive any payment in respect thereof. For more information, please see the sections titled “Risks Related to the CCRs” and “CCR Agreement” beginning on pages 54 and 217, respectively, of this proxy statement/prospectus.

The Contribution Agreement (see page 216)

Concurrently with the effective time of the GP merger, ETC, ETE and ETE GP will execute a Contribution, Conveyance and Assumption Agreement (the “contribution agreement”) to effect the WMB Contribution and GP Contribution. In exchange for the contribution by ETC of substantially all of the assets and liabilities it assumed from WMB through the merger to ETE in the WMB Contribution, ETE will issue to ETC a number of ETE Class E units equal to (i) the number of ETC common shares issued to the WMB stockholders in the merger plus (ii) the number of ETC common shares issued to ETE in consideration for the Parent Cash Deposit.

The contribution agreement will also provide that ETE will indemnify ETC against all losses suffered or incurred by ETC after the effective date resulting from the consummation of the merger or the other transactions contemplated by the contribution agreement, as well as all losses (other than income taxes) suffered or incurred by ETC before or after the date of the contribution agreement. In addition, pursuant to the contribution agreement, ETE will indemnify ETC for any taxes incurred by ETC for each taxable year ending on or before December 31, 2018.

Recent Developments

Crude oil prices in the United States (based on NYMEX trading prices) have experienced a significant decline recently, dropping from an average of $60.00 per barrel in June 2015 to an average closing price of $37.96 in March 2016. Natural gas prices in the United States (based on NYMEX trading prices) also have experienced a significant decline, dropping from an average of near $3.00 per MMcf in June 2015 to an average closing price of $1.81 per MMcf in March 2016. Other energy commodity prices have also continued to decline or hover at relatively low levels. As a result, energy company equity values have declined sharply and credit has tightened. Equity and debt capital markets are less receptive and the cost of capital for energy companies, in general, is significantly more expensive than the cost of capital in June 2015. Most producers of oil and natural gas have recently reduced their levels of drilling and related projects to preserve existing liquidity and reduce financing needs in light of continued low prices and infrastructure constraints, as well as higher costs of capital. In some areas, producers are shutting-in production until realized prices improve as a result of higher energy prices and/or new infrastructure that improves netbacks. As a result of the current weak energy price environment and increased cost of capital, the industry in which WMB and ETE participate is likely to experience lower growth in terms of volumes, earnings, cash flows, cash distributions and dividends. Energy prices are highly variable and the industry in which WMB and ETE participate may experience lower or higher prices and those prices will effect volumes, earnings, cash flows, cash distributions and dividends.

As disclosed in “The Merger—Reasons of ETE’s General Partner’s Board for the Merger,” during its due diligence process relating to the merger, ETE identified significant commercial synergies ranging from new revenue opportunities, improved operational efficiencies and performance, new capital opportunities and prioritization of existing capital projects. At the time of execution of the merger agreement with WMB, ETE expected that the anticipated EBITDA from those commercial synergies would exceed $2 billion per year by 2020 and would require overall incremental capital investment of more than $5 billion to achieve. As part of ETE’s and WMB’s joint integration planning efforts, the management teams of both companies have devoted a significant amount of time in analyzing commercial synergy opportunities that may be achieved by the combined company following the closing of the merger. Taking into account facts and circumstances occurring since September 28, 2015, including those described in the preceding paragraph, ETE and WMB believe, as of March 23, 2016, that the base case for EBITDA from commercial synergies that is reasonably probable to be achieved by the combined company is approximately $126 million per year by 2020, which is materially less than the $2 billion of anticipated EBITDA from commercial synergies per year by 2020 identified by ETE as of September 28, 2015 and considered by the board of directors of ETE’s general partner when determining to approve entry into the merger agreement. The annual EBITDA that is reasonably probable of being achieved from commercial synergies by 2020 of $126 million is an amount determined by commercial development and finance personnel from ETE and WMB based on their analysis of commercial development projects that are reasonably probable to be successfully completed and based on, among other items, assumptions of WTI crude oil prices ranging from $32.92 per barrel in 2016 to $44.31 per barrel in 2020 and Henry Hub natural gas prices ranging from $2.34 per MMcf in 2016 to $3.11 per MMcf in 2020, which price assumptions were based on the forward price curve for futures contracts as of January 20, 2016. ETE and WMB also anticipate that the net capital savings to be incurred in connection with these commercial synergies would be approximately $220 million.

ETE and WMB also developed a case which assumed a recovery of crude oil and natural gas prices based on the forward price curve for futures contracts for these commodities as of July 22, 2015, which forward price curve indicated WTI crude oil futures prices ranging from $53.97 per barrel in 2016 to $64.26 per barrel in 2020 and Henry Hub natural gas futures prices ranging from $3.21 per MMcf in 2016 to $3.62 per MMcf in 2020. Based on these price assumptions, the commercial development and finance personnel from ETE and WMB determined that the annual EBITDA that may be potentially achieved by 2020 from commercial synergies would be approximately $590 million. ETE and WMB also anticipate that the net capital expenditures anticipated to be incurred to achieve these commercial synergies would be approximately $260 million. The commodity price assumptions related to the commercial synergies in this price recovery case are significantly higher than the average trading prices of these commodities as of the date of this proxy statement/prospectus and, as a result, ETE and WMB believe that the commercial synergies in this price recovery case may not be achieved.

The current range of anticipated EBITDA from commercial synergies jointly identified by ETE and WMB as described above in the base case and the price recovery case, however, is consistent with the range of potential synergies considered by WMB’s financial advisors when performing the analyses and arriving at the opinions described in “The Merger—Opinions of the Financial Advisors to the WMB Board.”

The section “The Merger—Financial Forecasts” contains certain prospective financial information for WMB and ETC as prepared by WMB and as made available to the legal and financial advisors of WMB and the WMB Board prior to the execution of the merger agreement. ETE did not review the projections for ETC prepared by WMB, and ETE makes no representations or warranties in respect thereof and such projections did not, at the time they were prepared, and do not currently, reflect the views of ETE. See “—Updated Financial Forecasts of ETC” below for updated financial forecasts of ETC provided by the management of ETE. As further noted in “The Merger—Financial Forecasts,” WMB does not intend to update or otherwise revise the prospective financial information contained therein to reflect the occurrence of subsequent events. WMB believes that the prospective financial information prepared by WMB, including forecasts for cash distributions per unit of ETC as described in “The Merger—Financial Forecasts—Pro Forma ETC Unaudited Financial Projections,” is no longer

valid, will likely be materially lower than reflected in the tables containing such prospective financial information and should not be relied upon in light of, among other things, the factors discussed in this “Recent Developments” section.

In addition to the factors described in this “Recent Developments” section, and as noted elsewhere in this proxy statement/prospectus, ETE has a significant amount of debt outstanding. As of March 31, 2016, ETE had approximately $6.4 billion of debt on a stand-alone basis and approximately $37.4 billion of consolidated debt, excluding the debt of its joint ventures. In addition, in connection with the merger, ETE expects to incur an additional $6.05 billion of debt to finance the cash portion of the merger consideration and to assume approximately $4.2 billion of outstanding debt under WMB’s senior notes. In light of the sustained low commodity price environment and ETE’s current leverage and credit profile, there is a risk that the incurrence and assumption of such additional debt could adversely affect ETE’s credit ratings. Any downgrade in ETE’s credit ratings following the transaction could adversely affect the investment grade credit ratings of ETP, SXL and WPZ, and the credit ratings of Sunoco. ETP, SXL and WPZ currently maintain investment grade ratings by Moody’s Investors Services, Inc. (“Moody’s”), Standard & Poor’s Rating Services (“S&P”) and Fitch Ratings, Inc. (“Fitch”). However, those current ratings may not remain in effect for any given period of time and a rating may be lowered or withdrawn entirely by a rating agency if, in its judgment, circumstances so warrant. If Moody’s, S&P or Fitch were to downgrade the long-term rating of any of the ETE Entities, particularly below investment grade, ETE’s consolidated borrowing costs could significantly increase, which would adversely affect ETE’s consolidated financial results, and the terms of ETE’s credit agreements could become significantly more restrictive. The potential pool of investors and funding sources could also decrease. Further, due to the relationship between ETE and the ETE Entities, any downgrade of ETE’s credit ratings could also result in a downgrade in one or more of the ETE Entities’ credit ratings. Ratings from credit agencies are not recommendations to buy, sell or hold ETE’s securities, and each rating should be evaluated independently of other ratings. In order for ETE to maintain its credit ratings at current rating levels, it may need to sell assets, issue additional equity securities, reduce cash distributions to unitholders or a combination thereof.

ETE states that in connection with ETE’s efforts to maintain its current credit ratings with Moody’s, S&P and Fitch, on March 8, 2016, ETE completed the private offering of Convertible Units to certain ETE common unitholders who are “accredited investors” (as defined in Regulation D promulgated under the Securities Act) (the “offerees”). The Convertible Units were issued to offerees who elected to participate in a plan (the “Plan”) to forgo a portion of their future potential cash distributions on ETE common units participating in the Plan for a period of up to nine fiscal quarters, commencing with distributions for the fiscal quarter ending March 31, 2016 (the “plan period”), and reinvest those distributions in the Convertible Units. Each offeree who elected to participate in the Plan (an “Electing Unitholder”) received one Convertible Unit for each ETE common unit that such Electing Unitholder validly elected to participate in the Plan (each such ETE common unit, a “Participating Common Unit”). With respect to each quarter for which the declaration date and record date occurs prior to the closing of the merger, or earlier termination of the merger agreement (the “WMB End Date”), each Participating Common Unit will receive the same cash distribution as all other ETE common units up to $0.11 per unit, which represents approximately 40% of the per unit distribution paid with respect to ETE common units for the quarter ended December 31, 2015 (the “Preferred Distribution Amount”), and the holder of such Participating Common Unit will forgo all cash distributions in excess of that amount (other than (i) any non-cash distribution or (ii) any cash distribution that is materially and substantially greater, on a per unit basis, than ETE’s most recent regular quarterly distribution, as determined by the ETE general partner (such distributions in clauses (i) and (ii), “Extraordinary Distributions”)). With respect to each quarter for which the declaration date and record date occurs after the WMB End Date, each Participating Common Unit will forgo all distributions for each such quarter (other than Extraordinary Distributions), and each Convertible Unit will receive the Preferred Distribution Amount payable in cash prior to any distribution on ETE common units (other than Extraordinary Distributions).

At the end of the plan period, each Convertible Unit will automatically convert into ETE common units, the number of which will be determined by dividing (a) the Conversion Value (as defined and described below) at the end of the plan period by (b) $6.56, which is 95% of the five-day volume-weighted average closing price of ETE common units on the NYSE on the date immediately prior to the commencement of the private offering (the “Conversion Price”).

The conversion value of each Convertible Unit (the “Conversion Value”) on the closing date of the offering is zero. The Conversion Value will increase each quarter in an amount equal to $0.285, which is the per unit amount of the cash distribution paid with respect to ETE common units for the quarter ended December 31, 2015 (the “Conversion Value Cap”), less the cash distribution actually paid with respect to each Convertible Unit for such quarter (or, if prior to the WMB End Date, each Participating Common Unit). Any cash distributions in excess of $0.285 per ETE common unit, and any Extraordinary Distributions, made with respect to any quarter during the plan period will be disregarded for purposes of calculating the Conversion Value.

ETE issued 329,299,267 Convertible Units to the Electing Unitholders at the closing of the offering, which represents the participation by common unitholders with respect to approximately 31.5% of ETE’s total outstanding common units. ETE’s Chairman, Kelcy L. Warren, participated in the Plan with respect to substantially all of his common units, which represent approximately 18% of ETE’s total outstanding common units, and was issued 187,313,942 Convertible Units. In addition, John McReynolds, a director of LE GP and President of LE GP; and Matthew S. Ramsey, a director of LE GP, ETP LLC and Sunoco GP LLC and President of ETP LLC, participated in the Plan with respect to substantially all of their common units, and Marshall S. McCrea, III, a director of LE GP, ETP LLC and SXL GP and the Group Chief Operating Officer and Chief Commercial Officer of LE GP, participated in the Plan with respect to a substantial portion of his common units. The common units for which Messrs. McReynolds, Ramsey and McCrea elected to participate in the Plan collectively represent approximately 2.2% of ETE’s total outstanding common units. ETE issued 21,382,155 Convertible Units to Mr. McReynolds, 51,317 Convertible Units to Mr. Ramsey and 1,112,728 Convertible Units to Mr. McCrea. In accordance with the ETE partnership agreement, the board of directors of LE GP determines the amount of cash available for distribution by ETE each quarter and the amount of the quarterly cash distribution to unitholders. Therefore, as directors of LE GP, each of Messrs. Warren, McReynolds, Ramsey and McCrea, together with the other directors of LE GP, exercise control over ETE’s distributions. Mr. Warren, as the owner of 81.2% of the membership interest in LE GP, has the ability to appoint and remove the directors of LE GP. Mr. Ray Davis, who owns the remaining 18.8% membership interests in LE GP, participated in the Plan with respect to substantially all of his ETE common units, which represents approximately 6.9% of ETE’s total outstanding common units, and was issued 72,042,486 Convertible Units. Other than Mr. Davis, no other Electing Unitholder owns a material amount of equity securities of ETE or its affiliates and neither Mr. Davis nor such other Electing Unitholders has the ability to exercise control over ETE’s distributions.

ETE expected cash distribution savings from the offering of Convertible Units that would allow ETE to reduce its outstanding debt. However, ETE no longer expects to pay cash distributions with respect to its common units following the closing of the merger until the quarter ending March 31, 2018, and therefore, does not expect to receive any cash distribution savings until such time from forgone distributions on Participating Common Units, or to repay any debt from such cash distribution savings. See the section titled “Additional Information about ETC—Business—Recent Developments of Energy Transfer Equity, L.P.” for additional information regarding the private offering and the terms of the Plan and the Convertible Units.

Initially, ETE intended to provide the opportunity to participate in the Plan to all of its common unitholders on substantially the same terms as the private offering. The merger agreement requires ETE and WMB to obtain the other party’s consent to take certain actions prior to the closing of the merger. ETE believes that the terms of

the merger agreement permitted ETE to provide the opportunity to participate in the Plan to all of its common unitholders. In order to offer participation in the Plan to all of its common unitholders, ETE would have been required to file a registration statement with the SEC relating to the public offering of the Convertible Units. Such a filing would require the consent of WMB’s independent registered accounting firm to the incorporation by reference in the registration statement of its report on WMB’s audited financial statements. However, after ETE advised WMB of ETE’s intention to pursue a public offering of the Convertible Units pursuant to the Plan, WMB declined to allow its independent registered accounting firm to provide the auditor consent required to be included in a registration statement for a public offering. As a result, in light of what ETE viewed as an important step to address potential cash needs (including to finance part of the consideration payable to WMB stockholders in the merger), ETE determined to conduct a private offering to certain accredited investors that was not subject to the SEC rules requiring the consent of WMB’s independent registered accounting firm. In connection with the proposed public offering, WMB advised ETE that WMB believed its consent was required under the merger agreement for the public offering and declined to consent. ETE believes that both the proposed public offering and the completed private offering are permitted by the terms of the merger agreement and as a result did not request WMB’s consent to pursue the private offering.

WMB has reviewed the terms of the Plan and the Convertible Units, and ETE’s description of the Plan and the Convertible Units, and believes that the Convertible Units offering required WMB’s consent under the merger agreement and that by proceeding without WMB’s consent, ETE violated the merger agreement. WMB filed lawsuits against ETE, LE GP and Mr. Warren in relation to the Convertible Units offering on April 6, 2016. The lawsuit against ETE and LE GP, which was filed in the Court of Chancery of the State of Delaware (C.A. No. 12168-VCG), alleges breach of the merger agreement and seeks, among other things, to unwind the private offering of Convertible Units. The lawsuit against Mr. Warren, which was filed in the District Court of Dallas County, Texas (Cause No. DC-16-03941), alleges tortious interference with the merger agreement in connection with the Convertible Units offering and seeks damages, among other things. See the section titled “Risk Factors—Risks Related to the Merger—ETE and WMB do not agree on whether ETE’s offering of the Convertible Units without WMB’s consent was a violation of the merger agreement, and WMB has filed lawsuits against ETE, LE GP and Mr. Warren in relation thereto” beginning on page 51 of this proxy statement/prospectus. ETE believes that the lawsuits are without merit and intends to vigorously defend its actions.

In addition to the issuance of the Convertible Units that ETE believes is a means to address the rating agency issues described in this proxy statement/prospectus, ETE and WMB have been analyzing the potential cost savings that may be realized with respect to general and administrative expenses as a result of the merger. In light of the decline in energy commodity prices, both ETE and WMB are also analyzing cost reductions that may be achieved on a standalone basis and, in this regard, WMB recently reduced its workforce by 10%.

ETE and WMB have also been analyzing other steps to reduce general and administrative expenses. ETE has determined that it will be necessary to consolidate corporate offices and headquarters of ETE and WMB in Dallas, Texas in order to achieve the appropriate overall reduction in general and administrative costs for the combined company and headquarters and, as a result, the current presence of WMB in Tulsa, Oklahoma and Oklahoma City, Oklahoma will need to be significantly reduced, particularly with respect to the finance, accounting, engineering and construction, legal, human resources and information technology functions, or potentially eliminated.

The WMB Board has carefully reviewed the developments in this section in connection with the continuing recommendation of a majority of the WMB Board to WMB stockholders to adopt the merger agreement. See the section titled “The Merger—Recommendation of the WMB Board and Its Reasons for the Merger” beginning on page 132 of this proxy statement/prospectus. In particular:

The WMB Board believes it is appropriate to continue to rely on the fairness opinions dated September 28, 2015 for purposes of its original decision to enter into the merger agreement. However, the WMB Board acknowledges that those fairness opinions only address fairness of the consideration to be received by WMB stockholders as of September 28, 2015 and the WMB Board no longer believes that the projections underlying those fairness opinions are valid. Accordingly, the WMB Board is not relying on those fairness opinions in evaluating its recommendation to Williams’ stockholders to adopt the merger agreement in light of the developments described in this section. After conferring with its legal advisors, the WMB Board does not believe that it is necessary to request updated fairness opinions from its financial advisors and does not believe that updated fairness opinions would materially assist the WMB Board in evaluating its recommendation to WMB stockholders to adopt the merger agreement. The WMB Board believes it has, with the assistance of WMB management and the WMB Board’s financial advisors, the necessary expertise to evaluate the impact of changed economic conditions on the merits of the merger transaction.

After carefully reviewing the developments described in this section, including those noted above, the WMB Board has not changed its recommendation from its vote on September 28, 2015 that WMB stockholders adopt the merger agreement. Except as described below, the reasons for the WMB Board’s recommendation continue to be those described in the section titled “The Merger—Recommendation of the WMB Board and Its Reasons for the Merger” beginning on page 132 of this proxy statement/prospectus. These reasons include the value certainty provided by the substantial portion of the merger consideration that is payable in cash, the industrial logic of a combination of WMB’s and ETE’s businesses, that the WMB stockholders will have an opportunity to participate in the value created by the combination, the WMB Board’s assessment of WMB’s challenges as a standalone company, the strategic review process conducted by the WMB Board and the protective measures that were negotiated by the WMB Board regarding the economic equivalence of ETC common shares and ETE common units. As discussed above, the WMB Board continues to rely on the fairness opinions of WMB’s financial advisors dated September 28, 2015 for purposes of its original decision to enter into the merger agreement, but is not relying on such fairness opinions as a basis for the continuing recommendation of a majority of the WMB Board to WMB stockholders to adopt the merger agreement. The following reasons for the WMB Board’s recommendation described in the section titled “The Merger—Recommendation of the WMB Board and Its Reasons for the Merger” beginning on page 132 of this proxy statement/prospectus no longer serve as a basis for the continuing recommendation of a majority of the WMB Board that WMB stockholders adopt the merger agreement:

The WMB Board also notes that changes in the industries in which WMB and ETE operate and market conditions could adversely impact the likelihood of (i) ETC common shares being included in the S&P 500 Index and (ii) the merger resulting in the establishment of the third largest energy franchise in North America and one of the five largest global energy companies.

Certain members of the WMB Board voted on September 28, 2015 against entering into the merger agreement and continue to disagree with the recommendation of a majority of the WMB Board that WMB stockholders adopt the merger agreement. See section titled “The Merger—Background of the Merger” beginning on page 104 of this proxy statement/prospectus. Notwithstanding their continuing disagreement with the recommendation of the majority of the WMB Board, these directors fully support the WMB Board’s commitment to consummate the transaction as required by the terms of the merger agreement. The WMB Board is unanimously committed to enforcing WMB’s rights under the merger agreement and delivering the benefits of the merger agreement to WMB stockholders.

In connection with the merger, there are two other separate transactions that are occurring: (i) the transfer of newly issued ETC common shares from ETC to ETE in exchange for cash (to be used by ETC to fund the cash portion of the merger consideration) and (ii) the transfer by ETC of substantially all of the assets and liabilities it assumes from WMB in the merger to ETE in exchange for newly issued ETE Class E units (i.e., the WMB Contribution). Completion of the merger is subject to satisfaction or waiver of a number of conditions, including the receipt by ETC and WMB of the 721 Opinion from Latham.

Latham has recently advised ETE that it has concluded that there is a substantial risk that the IRS could successfully assert that the WMB Contribution would not be a transaction to which Section 721(a) of the Code applies based, in part, on the belief that the decline in value of ETE’s common units since the merger agreement was executed has increased such risk. In arriving at this conclusion, Latham considered and discussed with ETE claims that the IRS could possibly assert regarding whether the WMB Contribution would not be a transaction to which Section 721(a) of the Code applies, including the possibility that the IRS would successfully disregard the form of the transaction by applying various principles under statutory and case law (including Section 707 of the Code) and, therefore, assert that a portion of the cash consideration being paid by ETE for ETC common shares may be deemed paid by ETE to ETC for the Williams assets in the WMB Contribution. Accordingly, considering the potential claims that the IRS may successfully assert and the level of uncertainty regarding the ultimate outcome of these claims, Latham has advised ETE that it would not be able to deliver the 721 Opinion were the opinion requested as of the date of this proxy statement/prospectus.

The ability of Latham to deliver the 721 Opinion is also dependent on ETE not being treated as an investment company for federal income tax purposes if ETE were incorporated. ETE has received favorable private letter rulings from the IRS that address material legal issues with respect to ETE not being treated as an investment company for federal income tax purposes if ETE were incorporated. Accordingly, Latham does not believe that this issue will affect its ability to deliver the 721 Opinion.

After Latham advised ETE that it would not be able to deliver the 721 Opinion as described above, ETE consulted not only with Latham, but also with other legal advisors, regarding the risks that the WMB Contribution would not be a transaction to which Section 721(a) of the Code applies. Following those consultations and based on the information available to it, ETE believes that there is a substantial risk that the WMB Contribution will not be a transaction to which Section 721(a) of the Code applies given the risk that the IRS will successfully disregard the form of the transaction by applying various principles under statutory and case law (including Section 707 of the Code) and, therefore, assert that a portion of the cash consideration being paid by ETE for ETC common shares will be deemed paid by ETE to ETC for the WMB assets in the WMB Contribution.

ETE has also considered WMB’s views. On advice of Cravath, special counsel to WMB in connection with the transaction, WMB has advised ETE that it disagrees with Latham’s position and that it believes the WMB Contribution should be a transaction to which Section 721(a) of the Code applies. Further, in an effort to address ETE’s concerns, WMB has proposed two alternative transaction structures, each of which WMB and Cravath believe fully address ETE’s concerns. On advice of Cravath, WMB believes that the covenants in the merger agreement that require the parties to use commercially reasonable efforts to cause the WMB Contribution to qualify as an exchange to which Section 721(a) of the Code applies and to obtain the 721 Opinion require ETE and WMB to restructure the existing transaction in a manner such as WMB has suggested. ETE has advised WMB that it does not believe, after consultation with its legal advisors, that the merger agreement requires ETE to restructure the existing transaction as WMB has proposed. ETE has further advised WMB that, reserving its rights to assert that restructuring of the existing transaction is not required under the merger agreement, it has discussed the alternative transaction structures proposed by WMB and that, after consulting with Latham and the other legal advisors and based on their advice, ETE has concluded that there is a substantial risk that the form of either of the proposed alternative transaction structures, if undertaken would not be respected for tax purposes and, therefore, that there would remain the substantial risk of material taxation described above.

ETE is continuing to evaluate the tax risks referred to above and has expressed its willingness to continue to discuss the matter with WMB. Further, although ETE is fully committed to meeting its obligations under the merger agreement and using its reasonable best efforts to have the registration statement on Form S-4 declared effective so that WMB may proceed to a stockholder meeting to vote on the merger, ETE believes that there is a substantial risk that the closing condition relating to the 721 Opinion will not be met. Because ETE believes that ETE and ETC will be materially adversely affected if the WMB Contribution is not an exchange to which Section 721(a) of the Code applies, it is unlikely that ETC would waive the condition to closing that ETC receive the 721 Opinion from Latham. Based on the information available to WMB as of the date of this proxy statement/prospectus, WMB believes that the WMB Contribution should qualify as an exchange to which Section 721(a) of the Code applies. WMB is, therefore, willing to waive the condition to closing that WMB receive the 721 Opinion from Latham. In addition, on May 13, 2016, WMB filed a lawsuit against ETE in the Delaware Court of Chancery seeking, among other remedies, a declaratory judgment and injunction preventing ETE from terminating or otherwise avoiding its obligations under the merger agreement due to any failure of Latham to deliver the 721 Opinion to ETC and WMB. ETE believes that the allegations underlying the lawsuit are without merit and intends to vigorously defend against them. Please see “Recent Developments—Litigation Related to the 721 Opinion and the Outside Date.”

Currently, neither ETE nor WMB has an estimate as to when the WMB stockholders are likely to learn the outcome of this issue, nor can either party provide any assurance that the outcome of this issue will be determined prior to the special meeting. If the closing condition relating to the 721 Opinion is not met or waived, and as a result the merger is not consummated, ETE expects to announce this outcome in a press release and file a Current Report on Form 8-K with the SEC regarding the same. See the section entitled “Risk Factors—Risks Related to the Merger—There is no assurance when or if the merger will be completed, and ETE believes there is substantial risk that the merger will not be consummated.”

Updated Financial Forecasts of ETC

In an effort to understand the effects of more challenging business conditions and the merger, management of ETE has prepared projections for ETC, on a pro forma basis after giving effect to the merger, and shared those projections with the board of directors of LE GP and with WMB. The projections were based upon facts and circumstances known to management of ETE as of April 12, 2016, were delivered to WMB on April 12, 2016, and have not been subsequently updated. The ETC projections were based in part on projected financial information prepared by WMB management with respect to WMB that was provided by WMB to ETE on April 7, 2016. In preparing the ETC projections, ETE made a variety of assumptions, as described below. WMB expressly takes no responsibility for the ETC projections and states no view on the reasonableness of such projections.

You should be aware that this forecasted financial information is based on numerous assumptions about future events, as further discussed below. Many of these assumptions are speculative in nature and actual results for ETC will likely vary materially in one manner or another from the forecast. Nevertheless, management of ETE believes the forecast was prepared on a reasonable basis.

Neither ETE’s nor WMB’s independent registered public accounting firm nor any other independent registered public accounting firm has compiled, examined or performed any procedures with respect to the forecasted financial information, nor do they take any responsibility whatsoever for the forecasted financial information. You should consider that ETC and ETE are the only parties responsible for the inclusion herein of the following forecasted financial information.

Pro Forma Forecasted Financial Information

In developing the forecasted financial information set forth above, management of ETE made numerous material assumptions with respect to WMB, ETE and ETC for the periods covered by the projections, and management of WMB made numerous material assumptions with respect to the information related to WMB that ETE management utilized in preparing the forecasted financial information set forth above, including:

ETE management has assumed in preparing the forecasted financial information set forth above that, commencing with the distributions related to the second quarter of 2016 for each of ETP and WPZ payable on or before August 15, 2016, ETE will agree to waive incentive distributions to which it would otherwise be entitled from each of ETP and WPZ in amounts intended to permit each of ETP and WPZ to maintain their respective investment grade credit ratings without reducing distributions payable with respect to ETP’s or WPZ’s common units. Accordingly, the assumptions underlying the projections with respect to the availability and cost of debt and equity capital to ETP and WPZ during the projection period assume that ETP and WPZ maintain distributions at their respective current levels through 2016 and 2017 and ETP increases distributions in 2018

while WPZ maintains the same, and that ETP and WPZ maintain their respective investment grade credit ratings. While ETE believes these assumptions are reasonable, there can be no assurances that the board of directors of LE GP will ultimately approve incentive distribution waivers in such amounts or at all or that any incentive distribution waivers will permit ETP or WPZ to maintain their respective investment grade credit ratings (with or without reducing distributions payable with respect to their respective common units).

In preparing the forecasted financial information set forth above, ETE management has also assumed that all of the cash distributions that it receives from ETP, WPZ, SXL and SUN following the closing of the merger through mid-2018, after taking into account the waivers of incentive distributions assumed to be agreed to by ETE as described above, will be used to make cash distributions on the Convertible Units and to repay a portion of the indebtedness incurred by ETE in connection with the merger. As a result, ETE does not expect to make any cash distributions with respect to its common units or Class E Units prior to the distribution payable with respect to the quarter ending March 31, 2018. Assuming ETE does not pay any distributions on its common units and pays a distribution of $0.11 per unit with respect to its Convertible Units for each quarter during the forecast period, the Conversion Value at the end of the plan period for each Convertible Unit and for all of the Convertible Units issued in the offering would be $1.575 and approximately $518.6 million, respectively. Upon conversion of the Convertible Units at the end of the plan period, each Convertible Unit would convert into approximately 0.24 ETE common units, resulting in an aggregate issuance of approximately 79.1 million ETE common units. Assuming that ETE does not issue any additional equity securities prior to the end of the plan period, upon the conversion of the Convertible Units, ETC would own an approximate 55% limited partner interest in ETE, which is less than the approximate 57% limited partner interest in ETE that ETC will hold immediately following the completion of the merger transactions. The Convertible Units have a priority distribution over the ETE common units and, following the merger, will have a priority distribution over the ETE Class E Units. Thus, ETE’s unitholders that did not participate in the offering (including ETC, as the future holder of ETE Class E Units) may not receive any cash distributions with respect to their units, including in any quarter in which holders of the Convertible Units receive a cash distribution and/or an increase in the Conversion Value of their Convertible Units. If ETE does not make a cash distribution on its common units, then ETC will not receive a cash distribution on the ETE Class E Units that it will own following the merger and will not have any cash available for distribution on its common shares.

ETE expected cash distribution savings from the offering of Convertible Units that would allow ETE to reduce its outstanding debt. However, ETE no longer expects to pay cash distributions with respect to its common units following the closing of the merger until the quarter ending March 31, 2018, and therefore, does not expect to receive any cash distribution savings until such time from forgone distributions on Participating Common Units, or to repay any debt from such cash distribution savings. As described above, ETE expects to reduce its outstanding debt following the merger with cash distributions it receives from ETP, WPZ, SXL and SUN through mid-2018. As a result, ETE expects that it will be able to reduce its unconsolidated leverage ratio to approximately 3.7x for the year ending December 31, 2018 and ETE believes that its overall plan to reduce its unconsolidated leverage ratio to this level will position ETE to maintain its current debt rating throughout the forecast period.

All of the above assumptions involve variables making them difficult to predict, and most are beyond the control of either WMB, ETE or ETC. Although management of WMB and ETE, as applicable, believe that there was a reasonable basis for their respective internal projections and the underlying assumptions related thereto, any assumptions for near-term and long-term projected cases remain uncertain, and the risk of inaccuracy increases with the length of the forecasted period.

Litigation Relating to the Convertible Unit Offering

On April 6, 2016, WMB filed a complaint, accompanied by a motion for expedited proceedings, against ETE and LE GP in the Delaware Court of Chancery. The complaint is captioned The Williams Companies, Inc. v. Energy

Transfer Equity, L.P., et al., C.A. No. 12168-VCG. WMB alleges that ETE has breached the merger agreement by making the private offering of Convertible Units, as announced in a Current Report on Form 8-K filed by ETE on March 9, 2016. As relief, WMB seeks, among other things, to unwind the private offering and invalidate Amendment No. 5 to the ETE partnership agreement, adopted on March 8, 2016 (the “Amendment”), pursuant to which ETE established the Convertible Units. On April 14, 2016, the Court granted WMB’s motion for expedited proceedings in a ruling from the bench. The Court has ordered that the injunction hearing for this lawsuit be held during the week of June 13, 2016. Therefore, while this lawsuit may not be resolved prior to the special meeting, WMB has advised ETE that it expects that the lawsuit will be resolved prior to the consummation of the merger. Also on April 6, 2016, WMB filed a petition against Mr. Warren, the chairman of ETE, in the District Court of Dallas County, Texas, captioned The Williams Companies, Inc. v. Warren, No. DC-16-03941. In the Warren action, WMB alleges that Mr. Warren has tortiously interfered with the merger agreement by inducing ETE to undertake the private offering, and seeks compensatory damages, exemplary damages and other relief. The exact amount of damages is a factual issue to be determined at trial if the case should reach trial. The Warren action is a suit against Mr. Warren individually. Therefore, WMB believes any judgment would be satisfied out of Mr. Warren’s personal funds and would not require payment by ETE or ETC unless Mr. Warren is entitled to indemnification from ETE pursuant to the provisions of the ETE partnership agreement or the separate directors and officers indemnification agreement between ETE and Mr. Warren. WMB has advised ETE that it believes the Warren action will likely not be resolved prior to the special meeting or the consummation of the merger.

On May 3, 2016, ETE and LE GP filed an answer and counterclaim. The counterclaim asserts that WMB materially breached its obligations under the merger agreement by (i) blocking ETE’s attempts to complete a public offering of the Convertible Units pursuant to the Plan, including, among other things, by declining to allow WMB’s independent registered public accounting firm to provide the auditor consent required to be included in the registration statement for a public offering and (ii) bringing the Warren action against Mr. Warren in the District Court of Dallas County, Texas. WMB believes that ETE and LE GP’s counterclaim is without merit and intends to defend against it vigorously.

ETE has advised WMB that it believes the action against ETE is without merit and that the action is harmful to the merger process. Mr. Warren and ETE have both advised WMB that they believe the action against Mr. Warren is without merit, that it is harmful to the merger process, particularly since WMB is claiming that Mr. Warren, who will control ETC following the closing of the merger, acted in a materially wrongful manner, and that ETE will likely be required to indemnify Mr. Warren against all costs and other payments resulting from the Warren action. ETE believes that the lawsuit against Mr. Warren violates the terms of the merger agreement, including the parties’ agreement to file any lawsuits relating to the merger agreement in the Court of Chancery in the State of Delaware, and that WMB brought the suit against Mr. Warren at least in part to pressure ETE to resolve the action WMB has brought against ETE. WMB believes that the merger agreement’s requirement to bring suit in the Court of Chancery in the State of Delaware is inapplicable to the lawsuit against Mr. Warren because, among other things, the lawsuit is against Mr. Warren individually and Mr. Warren is not a party to the merger agreement.

ETE is unable at this time to determine when these actions will be resolved. While ETE and Mr. Warren believe they are meritless, ETE believes that if the actions are resolved adversely to ETE or Mr. Warren such resolution could have a material adverse impact on the operations and financial condition of ETC following the merger and, with regard to Mr. Warren, if ETE is not required to indemnify Mr. Warren (which is contrary to ETE’s and Mr. Warren’s belief), Mr. Warren could be required to sell some or all of his ETE common units or his ownership interests in LE GP or ETC GP, to fund any damage award. Any sale of a significant amount of ETE common units by Mr. Warren could have a substantial negative impact on the trading price of ETE common units following the merger, and any sale of Mr. Warren’s interests in LE GP or ETC GP could result in a change of control of ETC and ETE (which, in the case of ETE, could trigger change of control repurchase obligations under its senior notes and an immediate event of default under its credit facilities entitling the lenders thereunder to accelerate repayment or pursue other remedies) and significant disruption in their respective businesses and

operations, any of which could have a negative impact on ETE, ETC and their respective equityholders. Mr. Warren is permitted to sell his interests in LE GP and ETC GP without any approval by ETE or ETC or their respective equityholders. Immediately after the closing of the merger, the actions against ETE, LE GP and Mr. Warren would be contributed from ETC to ETE as part of the WMB Contribution. Accordingly, after closing, ETE will have the right to determine whether to proceed with such actions based on the best interests of the ETE unitholders and the ETC shareholders at such time.

On April 12 and 22, 2016, two purported ETE unitholders filed putative class action lawsuits against ETE, LE GP, LE GP directors and certain recipients of the Convertible Units, captioned Levine v. Energy Transfer Equity, L.P., et al. and Bowood MLP Return Fund, L.P. v. Energy Transfer Equity, L.P., both in the Delaware Court of Chancery. The Bowood plaintiff had previously filed a books and records action on April 11, 2016 in the Delaware Court of Chancery but dismissed this action when it filed the Bowood lawsuit. The complaints allege that the defendants breached various provisions of ETE’s limited partnership agreement due to ETE’s issuance of the Convertible Units. The Bowood complaint also alleges causes of action for unjust enrichment and tortious interference with ETE’s limited partnership agreement in connection with ETE’s issuance of the Convertible Units. The complaints seek, among other things, to enjoin ETE from making distributions on the Convertible Units and to invalidate the Amendment. On April 22, 2016, the Court granted the Levine plaintiff’s motion for expedited proceedings and ordered the parties to negotiate a schedule so that a preliminary injunction hearing can be held by early August 2016. The parties are currently negotiating a scheduling order per the Court’s instructions, and the Bowood plaintiff has moved to consolidate its lawsuit with the Levine lawsuit. The defendants believe the allegations in the complaints are without merit and intend to vigorously defend their actions.

Amendment of the Merger Agreement

On and effective as of May 1, 2016, the parties to the merger agreement approved an amendment to the merger agreement (the “amendment”) to remove the requirement that the Election Deadline be at least 30 days prior to the anticipated closing date of the merger, and provide instead that the Election Deadline will be the earlier of (i) the 20th business day after the Mailing Date and (ii) three business days prior to the anticipated closing date of the merger. The amendment also removes the requirement in the merger agreement that the election form be mailed to WMB stockholders of record at least 20 business days before the Election Deadline, and provides instead that the election form be mailed on the same date as this proxy statement/prospectus.

Litigation Relating to the 721 Opinion and Outside Date

On May 13, 2016, WMB filed a new lawsuit against ETE in the Delaware Court of Chancery. The lawsuit is captioned The Williams Companies, Inc. v. Energy Transfer Equity L.P., Energy Transfer Corp LP, ETE Corp GP, LLC, LE GP, LLC and Energy Transfer Equity GP, LLC. WMB alleges that ETE has breached the merger agreement by failing to cooperate to obtain the 721 Opinion from Latham and failing otherwise to use its reasonable best efforts to take all actions necessary to close the merger. As relief, WMB seeks, among other things, a declaratory judgment and injunction preventing ETE from terminating or otherwise avoiding its obligations under the merger agreement based on either (i) any failure to obtain the 721 Opinion from Latham or (ii) any failure to close the transaction by the Outside Date of June 28, 2016.

ETE believes that the allegations are without merit and intends to vigorously defend against them. Specifically, ETE believes that it has complied with its covenants in the merger agreement, including those requiring ETE to use commercially reasonable efforts to obtain the 721 Opinion and to otherwise use reasonable best efforts to consummate the merger and related transactions. Please see “Summary—Recent Developments” for additional discussion regarding ETE’s efforts to obtain the 721 Opinion and ETE’s beliefs regarding the substantive tax risks associated with the transaction. At the time this suit was filed, the parties were in the midst of resolving the remaining comments from the staff of the SEC related to this proxy statement/prospectus which would facilitate the mailing of the proxy statement/prospectus for the purpose of soliciting WMB stockholder approval or a

meeting to vote on the merger in advance of the June 28, 2016 Outside Date. ETE believes and has informed WMB that, even assuming the WMB stockholders approve the merger, the merger will still not be able to close due to a failure of a closing condition, given the substantial risk that Latham will not be able to deliver the 721 Opinion prior to the Outside Date and ETC’s current expectation that it would not waive such condition. Accordingly, ETE believes this lawsuit is an attempt to gain undue leverage in, and undermine future discussions regarding, the pending merger and that this lawsuit therefore will likely result in further delay in mailing the proxy statement/prospectus.

On May 20, 2016, ETE filed its affirmative defenses and counterclaim. The parties have agreed to expedited proceedings, with a trial scheduled to be held June 20 and June 21, 2016.

Organizational Structure of ETC Prior to the Merger Transactions

The diagram below depicts the simplified structure of the mergers and reflects the ownership structure of ETC, ETE and WMB prior to the consummation of the mergers.

Organizational Structure of ETC Following the Merger Transactions

The diagram below depicts the simplified organizational structure of ETC as of the date of this proxy statement/prospectus, after giving effect to the completion of the merger transactions: