Heart-Piercer Bow is a uncommon Artifact — Equipment card from Khans of Tarkir (KTK), collector number 221. Current market price: $0.13 (foil $0.46), TCGplayer market prices via Scryfall.
Whenever equipped creature attacks, this Equipment deals 1 damage to target creature defending player controls. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)