Nightkin Ambusher is a uncommon Creature — Mutant Warrior card from Fallout (PIP), collector number 112. Current market price: $0.32 (foil $2.20), TCGplayer market prices via Scryfall.
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.) When this creature enters, target player gets four rad counters. This creature can't be blocked as long as defending player has a rad counter.