Basilisk Collar is a rare Artifact — Equipment card from Double Masters (2XM), collector number 233. Current market price: $6.19 (foil $7.31), TCGplayer market prices via Scryfall.
Equipped creature has deathtouch and lifelink. (Any amount of damage it deals to a creature is enough to destroy it. Damage dealt by this creature also causes you to gain that much life.) Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)