Exhibit 10.4

ASSIGNMENT AND ASSUMPTION

OF

REGISTRATION RIGHTS AGREEMENT

This Assignment and Assumption of Registration Rights Agreement (this Assignment) is
entered into this 1stday of April, 2009, between Eldorado
Resorts LLC, a Nevada limited liability company (the Assignor), and Eldorado HoldCo LLC, a Nevada limited liability company (the Assignee), and is consented to by NGA AcquisitionCo, LLC a Nevada limited liability company
(NGA).

WHEREAS, Assignor and NGA are parties to that certain Registration Rights Agreement dated
December 14, 2007 (the Agreement), wherein NGA is granted certain registration rights as more specifically set forth in the Agreement.

WHEREAS, the members of Assignor have contributed all their respective membership interests in Assignor to Assignee in
return for proportionate membership interests in Assignee in accordance with that certain Contribution Agreement of even date herewith.

WHEREAS, Assignor desires to assign all of its right, title and interest in the Agreement to Assignee, and Assignee
desires to assume all of Assignors duties, obligations and liabilities in the Agreement, as more specifically set forth herein.

NOW THEREFORE, for good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, Assignor
hereby transfers to Assignee, and Assignee hereby assumes, all of Assignors rights and obligations in the Agreement as follows:

1. Assignment. Assignor assigns, transfers, sets over and delivers to Assignee all of Assignors right, title
and interest in, to and under the Agreement.

2. Assumption. Assignee assumes all duties, obligations
and liabilities of Assignor arising under the Agreement and agrees to comply with and fully perform all of Assignors duties, obligations and covenants thereunder.

3. Consent. Subject to Section 2 above, NGA consents to Assignors assignment to Assignee of its rights
and obligations under the Agreement as set forth in this Assignment.

4. Further Assurances. Assignor,
Assignee and NGA will do, execute, acknowledge and deliver all acts, assignments, transfers, notices and assurances as may be reasonably required to evidence and perfect this Assignment.

5. Governing Law. This Assignment is governed by the laws of the State of Nevada.

6. Binding Effect. This Assignment is binding upon and inures to the benefit of Assignor, Assignee and NGA and
their respective successors.



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7. Counterparts. This Assignment may be executed in any number of
counterparts and by facsimile signatures with the same effect as if all of the parties hereto were to have physically signed the same document at the same time and at the same place. All counterparts shall be construed together and shall constitute
the Assignment.

IN WITNESS WHEREOF, Assignor and Assignee have executed, and NGA has consented to, this
Assignment as of the day and year first set forth above.



|                                                           |  |                                 |  |                                                         |  |     |  |                                
|---------------------------------------------------------- |  | ------------------------------- |  | ------------------------------------------------------- |  | --- |  | -------------------------------
|Assignor:                                                  |  |                                 |  | Assignee:                                              
|                                                           |  |                                
|Eldorado Resorts LLC, a
Nevada limited liability company   |  |                                 |  | Eldorado HoldCo LLC, a
Nevada limited liability company
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Donald L. Carano            |  |                                                         |  | By: |  | /s/ Donald L. Carano           
|                                                           |  | Donald L. Carano, Manager       |  |                                                         |  |     |  | Donald L. Carano, Manager      
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Gary L. Carano              |  |                                                         |  | By: |  | /s/ Gary L. Carano             
|                                                           |  | Gary L. Carano, Manager         |  |                                                         |  |     |  | Gary L. Carano, Manager        
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Raymond J. Poncia, Jr.      |  |                                                         |  | By: |  | /s/ Raymond J. Poncia, Jr.     
|                                                           |  | Raymond J. Poncia, Jr., Manager |  |                                                         |  |     |  | Raymond J. Poncia, Jr., Manager
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Thomas Reeg                 |  |                                                         |  | By: |  | /s/ Thomas Reeg                
|                                                           |  | Thomas Reeg, Manager            |  |                                                         |  |     |  | Thomas Reeg, Manager           
|                                                           |  |                                 | 
|Consented To, Agreed And Accepted:                         |  |                                 |  |                                                         |  |    
|                                                           |  |                                 | 
|NGA AcquisitionCo, LLC, a
Nevada limited liability company |  |                                 |  |                                                         |  |    
|                                                           |  |                                 | 
|NGA AcquisitionCo, LLC, a Nevada limited liability company |  |                                 |  |                                                         |  |    
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Tim Janszen                 |  |                                                         |  |     |  |                                
|                                                           |  | Tim Janszen, Manager            |  |                                                         |  |     |  |                                
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Ryan Langdon                |  |                                                         |  |     |  |                                
|                                                           |  | Ryan Langdon, Manager           |  |                                                         |  |     |  |                                
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Roger May                   |  |                                                         |  |     |  |                                
|                                                           |  | Roger May, Manager              |  |                                                         |  |     |  |                                
|                                                           |  |                                 |  |                                                        
|By:                                                        |  | /s/ Thomas Reeg                 |  |                                                         |  |     |  |                                
|                                                           |  | Thomas Reeg, Manager            |  |                                                         |  |     |  |                                



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