Battlesong Berserker is a uncommon Creature — Human Berserker card from Foundations (FDN), collector number 78. Current market price: $0.17 (foil $0.26), TCGplayer market prices via Scryfall.
Whenever you attack, target creature you control gets +1/+0 and gains menace until end of turn. (It can't be blocked except by two or more creatures.)