Arni, Renowned Champion is a uncommon Legendary Creature — Human Berserker card from Reality Fracture (FRA), collector number 243. Current market price: $0.15 (foil $0.25), TCGplayer market prices via Scryfall.
Trample Whenever another creature you control enters, Arni gets +X/+0 until end of turn, where X is that creature's power.