I'm pretty sure I know the answer but want to double check. If I have Grave Betrayal out and a creature an opponent controls during my end step, do I need to wait until their end step to gain control of that creature since the card words it as "next end step"? Makes sense that it's delayed but wanted to know for sure.
You have to wait. The trigger for Grave Betrayal happens at the beginning of an end step so if you are already in the end step you will have to wait for the next one.
Grave Betrayal question