Siege Striker is a uncommon Creature — Human Soldier card from Core Set 2021 (M21), collector number 37. Current market price: $0.15 (foil $0.17), TCGplayer market prices via Scryfall.
Double strike (This creature deals both first-strike and regular combat damage.) Whenever this creature attacks, you may tap any number of untapped creatures you control. This creature gets +1/+1 until end of turn for each creature tapped this way.