Nov 21 (Reuters) - Nyx Gaming Group Ltd NYX.V
* NYX Gaming Group limited announces amendment to arrangement agreement with Scientific Games and waiver of standstill
* Says NYX agreed to waive existing standstill with Scientific Games contained in agreement between NYX and Scientific Games
* Says waiver of standstill is effective immediately
* Says deal not approved at vote in Dec or not move forward, Scientific Games to commence contractual takeover offer to NYX shareholders