Slaughter Specialist is a rare Creature — Vampire Warrior card from Innistrad: Midnight Hunt Promos (PMID), collector number 122p. Current market price: $1.52 (foil $0.94), TCGplayer market prices via Scryfall.
When this creature enters, each opponent creates a 1/1 white Human creature token. Whenever a creature an opponent controls dies, put a +1/+1 counter on this creature.