Mace of the Valiant is a rare Artifact — Equipment card from Throne of Eldraine (ELD), collector number 314. Current market price: $0.29, TCGplayer market prices via Scryfall.
Equipped creature gets +1/+1 for each charge counter on this Equipment and has vigilance. (Attacking doesn't cause it to tap.) Whenever a creature you control enters, put a charge counter on this Equipment. Equip {3}