At the beginning of each combat, any opponent may sacrifice a creature. If a player does, tap Desecration Demon and put a +1/+1 counter on it.
3/14/2017 Players won’t know which player or planeswalker Desecration Demon will attack, if any, when deciding whether to sacrifice a creature.
3/14/2017 Each opponent in turn order may choose to sacrifice a creature, even if an opponent already chose to sacrifice a creature that combat. Desecration Demon will have a maximum of one +1/+1 counter put on it each combat, no matter how many creatures were sacrificed.