Kruin Striker is a common Creature — Human Warrior card from Avacyn Restored (AVR), collector number 143. Current market price: $0.03 (foil $0.25), TCGplayer market prices via Scryfall.
Whenever another creature you control enters, this creature gets +1/+0 and gains trample until end of turn. (It can deal excess combat damage to the player or planeswalker it's attacking.)