Horned Helm is a common Artifact — Equipment card from The List (PLST), collector number 5DN-132. Current market price: $0.36, TCGplayer market prices via Scryfall.
Equipped creature gets +1/+1 and has trample. {G}{G}: Attach this Equipment to target creature you control. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)