Rocksteady, Mutant Marauder is a rare Legendary Creature — Rhino Mutant card from Teenage Mutant Ninja Turtles Eternal (TMC), collector number 33. Current market price: $0.23, TCGplayer market prices via Scryfall.
Partner with Bebop, Skull & Crossbones (When this creature enters, target player may put Bebop into their hand from their library, then shuffle.) Trample Whenever another nontoken creature you control enters, put a +1/+1 counter on target creature.