Sardian Cliffstomper is a uncommon Creature — Minotaur Barbarian card from The Brothers' War (BRO), collector number 383. Current market price: $0.20 (foil $0.32), TCGplayer market prices via Scryfall.
As long as it's your turn and you control four or more Mountains, this creature gets +X/+0, where X is the number of Mountains you control.