ASSIGNMENT OF OVERRIDING ROYALTY (Multiple Assignees)

Exhibit 10.21

NOTICE OF CONFIDENTIALITY RIGHTS: IF YOU ARE A NATURAL PERSON, YOU MAY REMOVE OR STRIKE ANY OF THE FOLLOWING INFORMATION FROM THIS INSTRUMENT BEFORE IT IS FILED FOR RECORD IN THE PUBLIC RECORDS: YOUR SOCIAL SECURITY NUMBER OR YOUR DRIVER’S LICENSE NUMBER.

ASSIGNMENT OF OVERRIDING ROYALTY

(Multiple Assignees)

Energy & Exploration Partners, LLC whose address is P.O. Box 471428, Fort Worth, Texas 76147-1376, hereinafter called “Assignor”, for and inconsideration of the sum of TEN DOLLARS ($10.00) and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged by Assignor, does by these presents, GRANT, ASSIGN, TRANSFER and CONVEY unto the parties set forth below, hereinafter called the “Assignees”:

Oso+Toro Multistrategy Fund Series Interest of the SALI Multiseries Fund II 3(C1) LP, whose address is 6836 Austin Center Boulevard, Suite 320, Austin, Texas 78731;

Oso+Toro Multistrategy Fund (Tax Exempt) Segregated Portfolio of the SALI Multiseries Fund SPC Ltd, whose address is 6836 Austin Center Boulevard, Suite 320, Austin, Texas 78731;

Carl Lasner, an individual, whose address is 1225 Red Hawk Rd., Wimberley, TX 78678;

Zachary Burk Lowe, an individual, whose address is 4154 Santa Barbara Dr., Dallas, Texas 75214;

Jason Roberts, an individual, whose address is 3005 Amherst Ave., Dallas, TX 75225.

an overriding royalty interest (the “Overriding Royalty”), as described in Exhibit “A” attached hereto and made a part hereof for all purposes, in all oil, gas and other hydrocarbons produced, save and sold under the terms of the Oil and Gas Leases described in Exhibit “A” (the “Lease(s)”) covering the lands described therein located in Weld County, Colorado.

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The assignment of Overriding Royalty made herein is subject to the following terms, conditions and provisions:

TO HAVE AND TO HOLD the above described overriding royalty, together with all and singular the rights and appurtenances thereunto in anywise belonging unto Assignee, its successors and assigns forever; and Assignor does by these presents bind itself and its successors and assigns to warrant and forever defend all and singular, the Leases unto Assignee, its successors and assigns, against every person whomsoever lawfully claiming or to claim the same or any part thereof by, through or under Assignor, but not otherwise.

[Signature page follows.]

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IN WITNESS WHEREOF, the parties have executed this instrument as of the dates set forth in the acknowledgement certificates below, but it is effective as of the date of each Lease.

~ACKNOWLEDGEMENT~

STATE OF TEXAS

COUNTY OF TARRANT

The foregoing instrument was acknowledged before me on this 20 of August, 2012 by Hunt Pettit, President of Energy & Exploration Partners, LLC, a Delaware limited liability company, on behalf of said company.

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EXHIBIT A

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