X-23, Deadly Weapon is a uncommon Legendary Creature — Mutant Berserker Hero card from Marvel Super Heroes Commander (MSC), collector number 738. Current market price: $1.35 (foil $4.20), TCGplayer market prices via Scryfall.
Whenever another Mutant you control enters, put a +1/+1 counter on that creature and a +1/+1 counter on X-23.