Jackknight is a rare Artifact Creature — Cyborg Knight card from The List (Unfinity Foil Edition) (ULST), collector number 5. Current market price: — (foil $0.23), TCGplayer market prices via Scryfall.
Whenever another artifact you control enters, put a +1/+1 counter on this creature. If that artifact is a Contraption, this creature gains lifelink until end of turn.