Grimgrin, Corpse-Born is a mythic Legendary Creature — Zombie Warrior card from Multiverse Legends (MUL), collector number 41. Current market price: $2.06 (foil $4.93), TCGplayer market prices via Scryfall.
Grimgrin enters tapped and doesn't untap during your untap step. Sacrifice another creature: Untap Grimgrin and put a +1/+1 counter on it. Whenever Grimgrin attacks, destroy target creature defending player controls, then put a +1/+1 counter on Grimgrin.