Mace of the Valiant is a rare Artifact — Equipment card from Phyrexia: All Will Be One Commander (ONC), collector number 78. Current market price: $0.36, 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}