Gavel of the Righteous is a rare Artifact — Equipment card from Edge of Eternities Commander (EOC), collector number 55. Current market price: $0.27, TCGplayer market prices via Scryfall.
At the beginning of combat on your turn, put a charge counter on this Equipment. Equipped creature gets +1/+1 for each counter on this Equipment. As long as this Equipment has four or more counters on it, equipped creature has double strike. Equip—Pay {3} or remove a counter from this Equipment.