Steel Squirrel is a uncommon Artifact Creature — Squirrel card from Unstable (UST), collector number 162. Current market price: $0.39 (foil $10.18), TCGplayer market prices via Scryfall.
Whenever you roll a 5 or higher on a die, this creature gets +X/+X until end of turn, where X is the result. {6}: Roll a six-sided die.