The Masamune is a rare Legendary Artifact — Equipment card from Final Fantasy Promos (PFIN), collector number 264s. Current market price: — (foil $8.39), TCGplayer market prices via Scryfall.
As long as equipped creature is attacking, it has first strike and must be blocked if able. Equipped creature has "If a creature dying causes a triggered ability of this creature or an emblem you own to trigger, that ability triggers an additional time." Equip {2}