Prospectus Filed Pursuant to Rule 424(b)(3) (424b3)

SUMMARY

This summary highlights selected information included in this consent solicitation statement/information statement/prospectus and does not contain all of the information that may be important to you. Accordingly, you should read this entire consent solicitation statement/information statement/prospectus, including the annexes hereto and the other documents referred to or incorporated by reference herein, carefully and in their entirety. You may obtain the information about Eclipse that is incorporated by reference into this consent solicitation statement/information statement/prospectus without charge by following the instructions in the section entitled “ Where You Can Find More Information ” beginning on page 269. Each item in this summary includes a page reference directing you to a more complete description of that item in this consent solicitation statement/information statement/prospectus.

Information About the Companies (pages 67 and 207)

Eclipse Resources Corporation

2121 Old Gatesburg Road, Suite 110

State College, Pennsylvania 16803

Phone: (814) 308-9754

Eclipse is an independent exploration and production company engaged in the acquisition and development of oil and natural gas properties in the Appalachian Basin. As of September 30, 2018, Eclipse had assembled an acreage position approximating 196,500 net acres in Eastern Ohio and 44,400 net acres in Pennsylvania, which excludes any acreage currently pending title. Approximately 134,200 of Eclipse’s net acres are located in the Utica Shale fairway, which Eclipse refers to as the Utica Core Area, and approximately 14,500 of these net acres are also prospective for the highly liquids rich area of the Marcellus Shale in Eastern Ohio within what Eclipse refers to as its Marcellus Area. Eclipse is the operator of approximately 96% of its net acreage within the Utica Core Area and its Marcellus Area. Eclipse intends to focus on developing its substantial inventory of horizontal drilling locations during commodity price environments that will allow it to generate attractive returns and will continue to opportunistically add to this acreage position where it can acquire acreage at attractive prices. Eclipse was formed in 2014 and is incorporated in the State of Delaware.

Upon completion of the merger, Eclipse will change its name to Montage Resources Corporation, and thereafter the Eclipse common stock will trade on the NYSE under the symbol “MR”.

Everest Merger Sub Inc.

c/o Eclipse Resources Corporation

2121 Old Gatesburg Road, Suite 110

State College, Pennsylvania 16803

Phone: (814) 308-9754

Merger Sub, whose legal name is Everest Merger Sub Inc., is a direct, wholly owned subsidiary of Eclipse. Upon the completion of the merger, Merger Sub will cease to exist. Merger Sub was incorporated in Delaware on August 10, 2018 for the sole purpose of effecting the merger.

Blue Ridge Mountain Resources, Inc.

Blue Ridge Mountain Resources, Inc.

122 West John Carpenter Freeway, Suite 300

Irving, Texas 75039

Phone: (469) 444-1647

BRMR is an independent exploration and production company engaged in the acquisition, development and production of natural gas, NGLs and oil. BRMR is active in two of the most prolific unconventional shale resource plays in North America, the Marcellus and Utica Shales. As of September 30, 2018, BRMR held approximately 105,000 net surface leasehold acres in the Marcellus and Utica Shales in Ohio and West Virginia, approximately 97,000, or 93%, of which are undeveloped. Approximately 73% of BRMR’s total net surface acres in these areas are held by production. BRMR is the operator on approximately 98% of this net acreage and holds an average 81% working interest across the position within developed units.

The Merger and the Merger Agreement (page 133)

The terms and conditions of the merger are contained in the merger agreement, which is attached to this consent solicitation statement/information statement/prospectus as Annex A and is incorporated by reference herein in its entirety. Eclipse and BRMR encourage you to read the merger agreement carefully, and in its entirety, as it is the legal document that governs the merger .

The Eclipse board and BRMR board each has unanimously approved the merger agreement and the transactions contemplated by the merger agreement. Pursuant to the terms and subject to the conditions included in the merger agreement, Eclipse has agreed to acquire BRMR by means of a merger of Merger Sub with and into BRMR, with BRMR surviving the merger as a wholly owned subsidiary of Eclipse.

Merger Consideration (page 135)

As a result of the merger, each eligible share of BRMR common stock issued and outstanding immediately prior to the effective time of the merger will be converted into the right to receive 0.29506 of a share of Eclipse common stock, subject to adjustment as specified in the merger agreement (the merger consideration), after giving effect to the Eclipse reverse stock split.

BRMR stockholders will not be entitled to receive any fractional shares of Eclipse common stock in the merger, and no BRMR stockholders will be entitled to dividends, voting rights or any other rights in respect of any fractional shares of Eclipse common stock. BRMR stockholders that would have otherwise been entitled to receive a fractional share of Eclipse common stock will instead be entitled to receive, in lieu of fractional shares, an amount in cash, without interest, equal to the product of the volume weighted average price of Eclipse common stock for the five consecutive trading days immediately prior to the closing date as reported by Bloomberg, L.P. (adjusted to give effect to the Eclipse reverse stock split), multiplied by the fraction of a share of Eclipse common stock to which the holder would otherwise be entitled.

Risk Factors (page 52)

The merger and an investment in Eclipse common stock involve risks, some of which are related to the transactions contemplated by the merger agreement. You should carefully consider the information about these risks set forth under the section entitled “ Risk Factors ” beginning on page 52, together with the other information included or incorporated by reference in this consent solicitation statement/information statement/prospectus, particularly the risk factors contained in Eclipse’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017. BRMR stockholders should carefully consider the risks set out in that section before submitting their written consents. For additional information, see the section entitled “ Where You Can Find More Information ” beginning on page 269.

Treatment of BRMR Equity Awards (page 136)

The merger agreement provides for the following treatment of BRMR equity awards in the merger, consistent with the terms of the applicable BRMR equity plan and/or equity award agreement:

BRMR Restricted Stock Units

Each outstanding BRMR RSU will vest in full at the effective time of the merger. Each BRMR RSU is the equivalent of one share of BRMR common stock. Except as described below with respect to certain BRMR RSUs granted to directors of BRMR, each holder of outstanding BRMR RSUs will be entitled to elect, no later than five business days prior to the closing date, whether to receive in the merger for such BRMR RSUs (i) the merger consideration (including cash in lieu of fractional shares) for each share of BRMR common stock subject to such holder’s BRMR RSUs, (ii) cash equal to the product of (A) the number of shares of BRMR common stock subject to such holder’s BRMR RSUs multiplied by (B) (1) the closing price of Eclipse common stock on the NYSE on the closing date multiplied by (2) the exchange ratio, or (iii) a combination thereof, subject to applicable withholding taxes as provided in the merger agreement and the applicable award agreement. The foregoing does not apply to certain BRMR RSUs granted to directors of BRMR, the terms of which do not provide for such an election. Holders of these other BRMR RSUs will receive the merger consideration (including cash in lieu of fractional shares) for each share of BRMR common stock subject to such BRMR RSUs, after giving effect to an adjustment to the number of such BRMR RSUs in connection with the merger pursuant to the terms of the applicable award agreement, subject to applicable withholding taxes as provided in the merger agreement and the applicable award agreement.

BRMR Performance Interest Awards

Each holder of a BRMR PIA will receive as a result of the merger in respect of such holder’s BRMR PIA:

in each case, subject to applicable withholding taxes as provided in the merger agreement and the applicable award agreement.

BRMR Restricted Stock

Each outstanding share of BRMR restricted stock will vest in full at the effective time of the merger, and the holders thereof will be entitled to receive the merger consideration (including cash in lieu of fractional shares) for such shares of BRMR restricted stock, subject to applicable withholding taxes as provided in the merger agreement and the applicable award agreement.

The Eclipse Board’s Reasons for the Merger (page 87)

The Eclipse board recommended that Eclipse stockholders approve the Eclipse stock issuance and the Eclipse charter amendment. For the factors considered by the Eclipse board in reaching this decision, see the section entitled “ The Merger—The Eclipse Board ’ s Reasons for the Merger ” beginning on page 87.

Recommendation of the BRMR Board and Reasons for the Merger (page 99)

The BRMR board unanimously recommends that you deliver a written consent to adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement. For a discussion of the factors considered by the BRMR board in reaching this decision and additional information on the recommendation of the BRMR board, see the section entitled “ The Merger—Recommendation of the BRMR Board and Reasons for the Merger ” beginning on page 99.

Opinions of Financial Advisors (pages 90 and 104)

Opinion of Jefferies, Eclipse’s financial advisor

In March 2018, Eclipse retained Jefferies LLC (which we refer to as “Jefferies”) to act as Eclipse’s financial advisor in connection with certain potential strategic transactions, including a possible acquisition by Eclipse or possible sale, disposition or other business transaction or series of related transactions involving all or a material portion of the voting securities or assets of Eclipse. At a meeting of the Eclipse board on August 23, 2018, a representative of Jefferies rendered Jefferies’ opinion to the Eclipse board to the effect that, as of that date and based upon and subject to the various assumptions made, procedures followed, matters considered and limitations on the scope of the review undertaken as set forth in its opinion, the exchange ratio as set forth in the merger agreement was fair, from a financial point of view, to Eclipse, as more fully described in the section of this consent solicitation statement/information statement/prospectus entitled “ The Merger— Opinion of Jefferies, Eclipse’s Financial Advisor ” beginning on page 90.

The full text of the written opinion of Jefferies, dated as of August 23, 2018, is attached hereto as Annex B. Jefferies’ opinion sets forth, among other things, the assumptions made, procedures followed, matters considered and limitations on the scope of the review undertaken by Jefferies in rendering its opinion. Eclipse encourages you to read Jefferies’ opinion carefully and in its entirety. Jefferies’ opinion was directed to the Eclipse board (in its capacity as such) and addresses only the fairness, from a financial point of view, to Eclipse of the exchange ratio as set forth in the merger agreement. It does not address the relative merits of the transactions contemplated by the merger agreement as compared to any alternative transaction or opportunity that might be available to Eclipse, nor does it address the underlying business decision by Eclipse to engage in the merger or the terms of the merger agreement or the documents referred to therein. Jefferies’ opinion does not constitute a recommendation as to how or whether any holder of Eclipse common stock should consent, vote or act with respect to the Eclipse stock issuance, the Eclipse charter amendment or any matter related thereto.

For additional information, see the section entitled “ The Merger—Opinion of Jefferies, Eclipse’s Financial Advisor ” beginning on page 90 and Annex B.

Opinion of Barclays, BRMR’s financial advisor

BRMR engaged Barclays Capital Inc. (which we refer to as “Barclays”) to act as its financial advisor with respect to the merger. On August 22, 2018, Barclays rendered its oral opinion (which opinion was subsequently confirmed in writing) to the BRMR board that, as of such date and based upon and subject to the qualifications, limitations and assumptions stated in its opinion, from a financial point of view, the exchange ratio to be offered to BRMR stockholders in the merger was fair to such stockholders, as more fully described in the section of this

consent solicitation statement/information statement/prospectus entitled “ The Merger— Opinion of Barclays, BRMR’s Financial Advisor ” beginning on page 104. The summary of Barclays’ opinion set forth below is qualified in its entirety by reference to the full text of Barclays’ written opinion.

The full text of Barclays’ written opinion, dated as of August 22, 2018, is attached as Annex C to this consent solicitation statement/information statement/prospectus. 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.

Barclays’ opinion was addressed to the BRMR board, addressed only the fairness, from a financial point of view, to BRMR stockholders of the exchange ratio to be offered to such stockholders and does not constitute a recommendation to any BRMR stockholder as to how such stockholder should vote with respect to the merger or any other matter. Barclays was not requested to opine as to, and its opinion did not in any manner address, BRMR’s underlying business decision to proceed with or effect the merger or the likelihood of the consummation of the merger. In addition, Barclays expressed no opinion on, and its opinion did not in any manner address, the fairness of the amount or the nature of any compensation to any officers, directors or employees of any party to the merger or any class of such persons, relative to the consideration to be offered to BRMR stockholders in connection with the merger. Barclays’ opinion did not address the relative merits of the merger as compared to any other transaction or business strategy in which BRMR might engage.

For additional information, see the section entitled “ The Merger—Opinion of Barclays, BRMR ’ s Financial Advisor ” beginning on page 104 and Annex C.

Eclipse Actions by Written Consent (page 68)

On August 23, 2018, the Eclipse board unanimously (i) determined that the merger agreement and the transactions contemplated thereby, including the Eclipse stock issuance pursuant to the merger agreement, and the Eclipse charter amendment, are fair to, and in the best interests of, Eclipse and its stockholders, (ii) approved and declared advisable the merger agreement and the transactions contemplated thereby, including the Eclipse stock issuance and the Eclipse charter amendment, (iii) directed that the approval of the Eclipse stock issuance and the Eclipse charter amendment be submitted to the Eclipse stockholders, and (iv) resolved to recommend that the Eclipse stockholders approve the Eclipse stock issuance and approve and adopt the Eclipse charter amendment. Eclipse stockholder approval is required for (x) the Eclipse stock issuance under the rules of the NYSE and (y) the Eclipse charter amendment under the Eclipse certificate of incorporation and the DGCL.

Pursuant to Section 228 of the DGCL and Section 2.14 of the Eclipse bylaws, any action required or permitted to be taken at any annual or special meeting of Eclipse stockholders may be taken without a meeting, without prior notice and without a vote of Eclipse stockholders, if a consent or consents in writing, setting forth the action so taken, is signed by the holders of outstanding stock having not less than the minimum number of votes that would be necessary to authorize or take such action at a meeting at which all shares entitled to vote thereon were present and voted. On August 25, 2018, the EnCap Entities, direct holders of an aggregate of 172,955,027 shares of Eclipse common stock, which comprised approximately 57.2% of the issued and outstanding shares of Eclipse common stock, as of August 23, 2018, executed and delivered the Eclipse stockholder written consent and thereby approved the Eclipse stock issuance and Eclipse charter amendment.

As a result of the Eclipse stockholder written consent, the requisite stockholder approval of the Eclipse stock issuance has been received as required under the rules of the NYSE, and the requisite stockholder approval of the Eclipse charter amendment has been received as required under the Eclipse certificate of incorporation and the DGCL. This consent solicitation statement/information statement/prospectus is furnished by Eclipse for the

purpose of informing and notifying Eclipse stockholders regarding the actions taken by the Eclipse stockholder written consent and is being provided pursuant to the requirements of Rule 14c-2 promulgated under Section 13 of the Exchange Act and Section  228(e) of the DGCL.

BRMR Solicitation of Written Consents (page 70)

BRMR is providing this consent solicitation statement/information statement/prospectus to its stockholders in connection with the solicitation of written consents to adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement.

The record date for the determination of BRMR stockholders entitled to execute and return written consents with respect to the consent solicitation contemplated by this consent solicitation statement/information statement/prospectus is January 9, 2019. Only BRMR stockholders of record at the close of business on the record date of January 9, 2019 will be entitled to execute and return written consents. As of the close of business on the record date, there were 50,882,938 shares of BRMR common stock outstanding and with respect to which the holders are entitled to execute and return written consents. As of the close of business on the record date, the directors and executive officers of BRMR beneficially owned and were entitled to execute and return written consents with respect to, in the aggregate, 352,171 shares of BRMR common stock, representing less than one percent of the shares of BRMR common stock outstanding on that date. Each holder of BRMR common stock is entitled to one vote for each share of BRMR common stock owned as of the close of business on the record date.

Under the DGCL, the merger agreement must be adopted by the affirmative vote of or consent with respect to a majority of the outstanding shares of BRMR common stock. In addition, the BRMR stockholders agreement prohibits BRMR from consummating a merger or taking certain other actions, including amending its certificate of incorporation and bylaws and changing the number of members of the BRMR board, each of which would occur upon consummation of the merger pursuant to the merger agreement, without the approval of the holders of a majority of the outstanding shares of BRMR common stock. Accordingly, the merger and the other transactions contemplated by the merger agreement require the same approval of BRMR stockholders as is required for the adoption of the merger agreement pursuant to the DGCL. BRMR stockholders are being asked to consent to the adoption of the merger agreement for purposes of the DGCL and the approval of the merger and the other transactions contemplated by the merger agreement for purposes of the BRMR stockholders agreement as a single proposal.

The parties to the BRMR voting agreement, representing approximately 60.7% of the outstanding shares of BRMR common stock, have agreed, subject to the terms of the BRMR voting agreement, to execute and return written consents adopting the merger agreement and approving the merger, the other transactions contemplated by the merger agreement and any actions related to the merger agreement within one business day after both the registration statement of which this consent solicitation statement/information statement/prospectus forms a part becomes effective under the Securities Act and this consent solicitation statement/information statement/prospectus has been delivered to such BRMR stockholders. The delivery of the written consents by the parties to the BRMR voting agreement will be sufficient to adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement.

Holders of shares of BRMR common stock as of the close of business on the record date may complete, date, and sign the written consent furnished with this consent solicitation statement/prospectus and promptly return it to BRMR by hand delivery or mail or by email of a .pdf copy to Blue Ridge Mountain Resources, Inc., 122 West John Carpenter Freeway, Suite 300, Irving, Texas 75039, Attention: Frank E. Day, Vice President and Corporate Counsel; Email: fday@brmresources.com. If your shares of BRMR common stock are held in “street name” through a bank, brokerage firm or other nominee, you should follow the instructions provided by your bank, brokerage firm or other nominee to ensure that consents with respect to your shares are properly delivered and counted.

BRMR has set 5:00 p.m., Irving, Texas time, on February 25, 2019 as the targeted final date for the receipt of written consents. BRMR reserves the right to extend the final date for the receipt of written consents beyond February 25, 2019 for any reason in its sole discretion. Among other reasons, BRMR may extend the final date for receipt of written consents if necessary in order to receive written consents and requests from holders of shares of BRMR common stock sufficient to cause the merger to be a drag transaction under the BRMR stockholders agreement. Any such extension may be made without notice to the BRMR stockholders, although BRMR currently expects that it would issue a press release or other public communication notifying the BRMR stockholders of any such extension. In addition, BRMR reserves the right to conclude the consent solicitation prior to February 25, 2019 if, prior to that date, BRMR has received written consents from holders of shares of BRMR common stock sufficient to (i) adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement and (ii) cause the merger to be a drag transaction under the BRMR stockholders agreement. Any such early conclusion of the consent solicitation may be made without notice to the BRMR stockholders, although BRMR currently expects that it would issue a press release or other public communication notifying the BRMR stockholders of any such early conclusion.

If you are a BRMR stockholder as of the close of business on the record date and you do not execute and return a written consent, your shares of BRMR common stock will not be voted with respect to the adoption of the merger agreement and approval of the merger and the other transactions contemplated by the merger agreement. Accordingly, failure to execute and return a written consent effectively will constitute a vote against adoption of the merger agreement and approval of the merger and the other transactions contemplated by the merger agreement.

The written consent accompanying this consent solicitation statement/information statement/prospectus provides the opportunity to elect to consent in favor of or against adoption of the merger agreement and approval of the merger and the other transactions contemplated by the merger agreement. If you execute and return your written consent but do not make a specific election, you will be deemed to have elected to consent in favor of adoption of the merger agreement and approval of the merger and the other transactions contemplated by the merger agreement.

After you execute and return your written consent, except as described below with respect to parties to the BRMR voting agreement, you may revoke your written consent or change your election at any time before BRMR receives written consents from holders of shares of BRMR common stock sufficient to adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement. Once BRMR has received written consents from holders of shares of BRMR common stock sufficient to adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement, consents may not be revoked and elections may not be changed. Because the delivery of the written consents by the BRMR stockholders party to the BRMR stockholders agreement will be sufficient to adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement, you will not be able to revoke your consent or change your election after the delivery of written consents by those BRMR stockholders. Those BRMR stockholders have agreed, subject to the terms of the BRMR voting agreement, to execute and return such written consents within one business day after both the registration statement of which this consent solicitation statement/information statement/prospectus forms a part becomes effective under the Securities Act and this consent solicitation statement/information statement/prospectus has been delivered to such BRMR stockholders.

If you are a BRMR stockholder that is a party to the BRMR voting agreement, your consent to adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement will be irrevocable.

At any time at which you are permitted to revoke your consent or change your election, you can do so by delivering a written notice stating that you revoke your consent or delivering a new written consent with a later

date, in either case to Blue Ridge Mountain Resources, Inc., 122 West John Carpenter Freeway, Suite 300, Irving, Texas 75039, Attention: Frank E. Day, Vice President and Corporate Counsel; Email: fday@brmresources.com.

Interests of Eclipse Directors and Executive Officers in the Merger (page 122)

Eclipse stockholders should be aware that the executive officers and directors of Eclipse have interests in the merger that may be different from, or in addition to, the interests of Eclipse stockholders generally. These interests are described in more detail in the section entitled “ The Merger—Interests of Eclipse Directors and Executive Officers in the Merger ” and “ The Merger—Executive Officer Severance Arrangements ” beginning on pages 122 and 128, respectively. The members of the Eclipse board were aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement, in approving the merger agreement and in determining to recommend that Eclipse stockholders approve the Eclipse stock issuance and the Eclipse charter amendment.

Board of Directors and Management of Eclipse and the Surviving Corporation Following Completion of the Merger (pages 123 and 248)

Prior to the effective time of the merger, Eclipse will take all actions necessary to cause the Eclipse board as of and immediately following the effective time of the merger to consist of a total of ten directors meeting certain independence standards and other qualifications as set forth in the merger agreement, five of whom shall be designated by Eclipse and five of whom shall be designated by BRMR. From and after the effective time of the merger, such directors will serve as such until their respective successors are duly elected or appointed and qualified or their earlier resignation or removal; provided, however, that one of the directors designated by BRMR will resign on the first anniversary of the effective time of the merger and the Eclipse board will be reduced to consist of a total of nine directors. For information regarding the persons expected to be the directors of Eclipse upon consummation of the merger, see the section entitled “ Management of Eclipse Upon Consummation of the Merger .”

Prior to the effective time of the merger, Eclipse will take all actions necessary to cause the officers of Eclipse as of and immediately following the effective time of the merger to be the individuals listed on the disclosure letter delivered by Eclipse to BRMR in connection with the merger agreement, or, in certain cases, a replacement for such individual. From and after the effective time of the merger, such officers will serve until their resignation or removal from office by the Eclipse board. Prior to the effective time of the merger, Eclipse will take all actions necessary to cause the resignation or removal of each officer of Eclipse who will not be an officer of Eclipse as of and after the effective time of the merger as provided in the merger agreement from all offices and positions held by such person with Eclipse or any of its subsidiaries, with such resignation or removal to be effective as of the effective time of the merger. For information regarding the persons expected to be the executive officers of Eclipse upon consummation of the merger, see the section entitled “ Management of Eclipse Upon Consummation of the Merger .”

At the effective time, the directors of the surviving corporation will be John Reinhart and Oleg Tolmachev, each to hold office in accordance with the certificate of incorporation and bylaws of the surviving corporation until their respective successors are duly elected or appointed and qualified or their earlier removal or resignation. At the effective time, the officers of the surviving corporation will be the individuals listed on the disclosure letter delivered by Eclipse to BRMR in connection with the merger agreement, or, in certain cases, a replacement for such individual. The executive officers of the surviving corporation upon consummation of the merger will be the same as the executive officers of Eclipse upon consummation of the merger. Each of such officers will hold office in accordance with the certificate of incorporation and bylaws of the surviving corporation until their respective successors are duly appointed or their earlier removal or resignation.

Interests of BRMR Directors and Executive Officers in the Merger (page 124)

In considering the recommendation of the BRMR board with respect to the merger agreement and the merger, BRMR stockholders should be aware that the executive officers and directors of BRMR have interests in the merger that may be different from, or in addition to, the interests of BRMR stockholders generally. These interests are described in more detail in the sections entitled “ The Merger—Interests of BRMR Directors and Executive Officers in the Merger ” and “ The Merger—Treatment of BRMR Equity Awards ” beginning on pages 124, and 127, respectively. The members of the BRMR board were aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement, in approving the merger agreement and in determining to recommend that BRMR stockholders adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement.

Conditions to the Completion of the Merger (page 166)

Each party’s obligation to complete the merger is subject to the satisfaction or waiver of the following mutual conditions:

The obligations of Eclipse and Merger Sub to complete the merger are subject to the satisfaction or waiver of further conditions, including:

The obligation of BRMR to complete the merger is subject to the satisfaction or waiver of the following additional conditions:

No Solicitation (page 150)

No Solicitation by Eclipse

Eclipse has agreed that, from and after August 25, 2018 until the effective time of the merger, or if earlier, the termination of the merger agreement in accordance with its terms, Eclipse and its officers and directors will, and will cause Eclipse’s subsidiaries and their respective officers and directors to, and will use their reasonable best efforts to cause the other representatives of Eclipse and its subsidiaries to, immediately cease, and cause to be terminated, any solicitation, encouragement, discussion or negotiations ongoing with any third party with respect to any inquiry, proposal or offer that constitutes, or would reasonably be expected to lead to, an Eclipse competing proposal (as such term is defined in the section entitled “ The Merger Agreement—No Solicitation; Changes of Recommendation—Definitions of Competing Proposals ” beginning on page 156).

Eclipse has also agreed that, except as expressly permitted by the merger agreement, from and after August 25, 2018 until the effective time of the merger, or if earlier, the termination of the merger agreement in accordance

with its terms, Eclipse and its officers and directors will not, and will cause Eclipse’s subsidiaries and their respective officers and directors not to, and will use their reasonable best efforts to cause the other representatives of Eclipse and its subsidiaries not to, directly or indirectly, initiate, solicit, propose, knowingly encourage, or knowingly facilitate any inquiry or the making of any proposal or offer that constitutes, or would reasonably be expected to result in, an Eclipse competing proposal.

No Solicitation by BRMR

BRMR has agreed that, from and after August 25, 2018 until the effective time of the merger, or if earlier, the termination of the merger agreement in accordance with its terms, BRMR and its officers and directors will, and will cause BRMR’s subsidiaries and their respective officers and directors to, and will use their reasonable best efforts to cause the other representatives of BRMR and its subsidiaries to, immediately cease, and cause to be terminated, any solicitation, encouragement, discussion or negotiations ongoing with any third party with respect to any inquiry, proposal or offer that constitutes, or would reasonably be expected to lead to, a BRMR competing proposal (as such term is defined in the section entitled “ The Merger Agreement—No Solicitation; Changes of Recommendation—Definitions of Competing Proposals ” beginning on page 156).

BRMR has also agreed that, except as expressly permitted by the merger agreement, from and after August 25, 2018 until the effective time of the merger, or if earlier, the termination of the merger agreement in accordance with its terms, BRMR and its officers and directors will not, and will cause BRMR’s subsidiaries and their respective officers and directors not to, and will use their reasonable best efforts to cause the other representatives of BRMR and its subsidiaries not to, directly or indirectly:

Notwithstanding the agreements described above, prior to, but not after, the receipt of the BRMR Stockholder Approval, BRMR and its representatives may engage in the second and third bullets directly above with any person if (i) BRMR receives an unsolicited bona fide written BRMR competing proposal from such person; and (ii) such BRMR competing proposal did not arise from or in connection with a breach of the obligations described directly above and in the section entitled “ The Merger Agreement—No Solicitation; Changes of Recommendation—No Solicitation by BRMR ” beginning on page 150; provided, however, that:

Changes of Recommendation (page 150)

Eclipse Restrictions on Changes of Recommendation

The Eclipse board may not effect an Eclipse recommendation change (as defined in the section entitled “ The Merger Agreement—No Solicitation; Changes of Recommendation—Eclipse: Restrictions on Changes of Recommendation ” beginning on page 152).

BRMR Restrictions on Changes of Recommendation

Subject to certain exceptions described below, the BRMR board may not effect a BRMR recommendation change (as defined in the section entitled “ The Merger Agreement—No-Solicitation; Changes of Recommendation—BRMR: Restrictions on Changes of Recommendation ” beginning on page 153).

BRMR: Permitted Changes of Recommendation and Permitted Termination to Enter into a Superior Proposal

Prior to, but not after, the receipt of the BRMR Stockholder Approval, in response to an unsolicited bona fide written BRMR competing proposal from a third party that did not arise from or in connection with a breach of the “no solicitation” obligations described above and in the section entitled “ The Merger Agreement—No Solicitation; Changes of Recommendation—No Solicitation by BRMR ,” the BRMR board or a committee thereof may effect a BRMR recommendation change or terminate the merger agreement if:

BRMR: Permitted Changes of Recommendation in Connection with Intervening Events

Prior to, but not after, the receipt of the BRMR Stockholder Approval, in response to a BRMR intervening event (as defined in the section entitled “ The Merger Agreement—No Solicitation; Changes of Recommendation— BRMR:  Permitted Changes of Recommendation in Connection with Intervening Events ” beginning on page 154) that occurs or arises after August 25, 2018 and that did not arise from or in connection with a breach of the merger agreement by BRMR, BRMR may effect a BRMR recommendation change if:

Termination (page 169)

Eclipse and BRMR may terminate the merger agreement and abandon the merger at any time prior to the effective time of the merger by mutual written consent of Eclipse and BRMR.

The merger agreement may also be terminated by either Eclipse or BRMR at any time prior to the effective time of the merger in any of the following situations:

In addition, the merger agreement may be terminated by Eclipse:

Further, the merger agreement may be terminated by BRMR:

Termination Fees (page 170)

Termination Fees Payable by Eclipse

The merger agreement requires Eclipse to pay BRMR a termination fee of $12 million (which we refer to as the “reverse termination fee”) if:

In no event will Eclipse be required to pay the reverse termination fee on more than one occasion. In addition, if both the termination fee (as defined below) and the reverse termination fee are payable pursuant to the merger agreement, no payment of the termination fee or the reverse termination fee will be required.

Termination Fees Payable by BRMR

The merger agreement requires BRMR to pay Eclipse a termination fee of (i) $18 million, if payable (A) in connection with a termination of the merger agreement by Eclipse due to a BRMR recommendation change in response to a BRMR intervening event, or (B) in connection with a termination of the merger agreement by Eclipse or BRMR due to a BRMR stockholder approval termination event and BRMR has effected a BRMR

recommendation change in response to a BRMR intervening event, or (ii) $12 million, if payable in any other circumstance (which, in each case, we refer to as the “termination fee”) if:

In no event will BRMR be required to pay the termination fee on more than one occasion. In addition, if both the termination fee and the reverse termination fee (as described above) are payable pursuant to the merger agreement, no payment of the termination fee or the reverse termination fee will be required.

Regulatory Approvals (page 160)

Although the merger agreement includes covenants of the parties with respect to the making of any required filings under the HSR Act and efforts to obtain the expiration or early termination of the waiting period under the HSR Act, Eclipse and BRMR have determined that no filing under the HSR Act is required in connection with the merger. Neither Eclipse nor BRMR is aware of any material governmental approvals or actions that are required for completion of the merger. It is presently contemplated that if any such additional material governmental approvals or actions are required, those approvals or actions will be sought.

For additional information, see the section entitled “ The Merger Agreement—HSR and Other Regulatory Approvals ” beginning on page 160.

Specific Performance; Remedies (page 172)

Eclipse, BRMR and Merger Sub have agreed that each will be entitled to an injunction or injunctions, or any other appropriate form of specific performance or equitable relief, to prevent breaches of the merger agreement and to enforce specifically the terms and provisions of the merger agreement.

Except in the case of fraud or a willful and material breach, the monetary remedies and the specific performance remedies set forth in the merger agreement will be the receiving party’s sole and exclusive remedy against the paying party.

Dissenters’ Rights of Appraisal (page 203)

Unless the merger constitutes a drag transaction under the BRMR stockholders agreement, holders of BRMR common stock have the right to dissent from the proposed merger and, subject to certain conditions provided for in Section 262 of the DGCL, to receive payment of the fair value of their BRMR common stock as determined by the Delaware Court of Chancery. BRMR stockholders will be bound by the terms of the merger unless the merger does not constitute a drag transaction and they dissent by complying with all of the requirements of the Delaware dissenters’ rights statute. See the section entitled “ Dissenters’ Rights of Appraisal ” beginning on page 203 for a summary of dissenters’ rights available to BRMR stockholders, which summary is not intended to be a complete statement of applicable Delaware law and is qualified in its entirety by reference to Section 262 of the DGCL which is set forth in its entirety as Annex D to this consent solicitation statement/information statement/prospectus.

Eclipse stockholders do not have dissenter’s or appraisal rights in connection with the merger.

Material U.S. Federal Income Tax Consequences of the Merger (page 175)

It is a condition to each of BRMR’s and Eclipse’s obligation to complete the merger that each receives a written opinion from its counsel to the effect that, on the basis of facts, representations and assumptions set forth or referred to in such opinions, for U.S. federal income tax purposes, the merger will qualify as a “reorganization” within the meaning of Section 368(a) of the Code.

Assuming the merger qualifies as a “reorganization,” U.S. holders of shares of BRMR common stock generally will not recognize any gain or loss upon receipt of Eclipse common stock in exchange for BRMR common stock in the merger, except that gain or loss will be recognized with respect to any cash received in lieu of a fractional share of Eclipse common stock. On the other hand, non-U.S. holders generally will be required to recognize gain or loss upon receipt of Eclipse common stock and cash in lieu of a fractional share, and the merger consideration will be subject to withholding at the rate of 15%. The U.S. federal income tax consequences of the merger are discussed in more detail in the section entitled “ Material U.S. Federal Income Tax Consequences of the Merger ” beginning on page 175. The discussion of the material U.S. federal income tax consequences contained in this consent solicitation statement/information statement/prospectus is intended to provide only a general discussion and is not a complete analysis or description of all potential U.S. federal income tax consequences of the merger that may vary with, or are dependent on, individual circumstances. In addition, it does not address the effects of any foreign, state or local tax laws, or federal tax laws other than U.S. federal income tax laws.

TAX MATTERS ARE COMPLICATED AND THE TAX CONSEQUENCES OF THE MERGER WILL DEPEND ON THE FACTS OF YOUR OWN SITUATION. YOU SHOULD CONSULT YOUR OWN TAX ADVISOR AS TO THE SPECIFIC TAX CONSEQUENCES AS A RESULT OF THE MERGER TO YOU IN YOUR PARTICULAR CIRCUMSTANCES.

Comparison of Stockholders’ Rights (page 193)

The rights of BRMR stockholders who receive shares of Eclipse common stock in the merger will be governed by the Eclipse certificate of incorporation and the Eclipse bylaws, rather than by the BRMR certificate of incorporation, the BRMR bylaws and the BRMR stockholders agreement. As a result, BRMR stockholders will have different rights once they become Eclipse stockholders due to the differences in the organizational documents of BRMR and Eclipse. The key differences are described in the section entitled “ Comparison of Stockholders’ Rights ” beginning on page 193.

Listing of Eclipse Common Stock; Halting of Trading of BRMR Shares (page 131)

If the merger is completed, the shares of Eclipse common stock to be issued in the merger will be listed for trading on the NYSE, and shares of BRMR common stock will cease to be traded on the OTC Grey. Upon completion of the merger, Eclipse will change its name to Montage Resources Corporation, and thereafter the Eclipse common stock will trade on the NYSE under the symbol “MR”.