Serpentine Basilisk is a uncommon Creature — Basilisk card from Onslaught (ONS), collector number 280. Current market price: $0.15 (foil $2.16), TCGplayer market prices via Scryfall.
Whenever this creature deals combat damage to a creature, destroy that creature at end of combat. Morph {1}{G}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)