If one player has two or more {Grave Betrayal} out in play, does anything stack? Do the +1/+1 counters stack? Thank you.
Nope. The creature will get just 1 counter since each Grave Betrayal tries to return a creature from the graveyard. Once the second one sees there's no longer a creature to return, it won't be able to do anything.
I have been wondering about that as well. :) thanks for sorting that out!
Not a problem! That's what I'm here for 👍