Hero's Blade is a uncommon Artifact — Equipment card from Dominaria United Commander (DMC), collector number 186. Current market price: $0.28, TCGplayer market prices via Scryfall.
Equipped creature gets +3/+2. Whenever a legendary creature you control enters, you may attach this Equipment to it. Equip {4} ({4}: Attach to target creature you control. Equip only as a sorcery.)