Gau, Feral Youth is a rare Legendary Creature — Human Berserker card from Final Fantasy Commander (FIC), collector number 152. Current market price: $0.52 (foil $2.49), TCGplayer market prices via Scryfall.
Rage — Whenever Gau attacks, put a +1/+1 counter on it. At the beginning of each end step, if a card left your graveyard this turn, Gau deals damage equal to its power to each opponent.