Tormentor's Helm is a common Artifact — Equipment card from Kaldheim (KHM), collector number 155. Current market price: $0.22 (foil $0.24), TCGplayer market prices via Scryfall.
Equipped creature gets +1/+1. Whenever equipped creature becomes blocked, it deals 1 damage to defending player. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)