Sarulf, Realm Eater is a rare Legendary Creature — Wolf card from Magic Online Promos (PRM), collector number 88370.
Whenever a permanent an opponent controls is put into a graveyard from the battlefield, put a +1/+1 counter on Sarulf. At the beginning of your upkeep, if Sarulf has one or more +1/+1 counters on it, you may remove all of them. If you do, exile each other nonland permanent with mana value less than or equal to the number of counters removed this way.