Buster Sword is a mythic Artifact — Equipment card from Final Fantasy Promos (PFIN), collector number 255s. Current market price: — (foil $110.68), TCGplayer market prices via Scryfall.
Equipped creature gets +3/+2. Whenever equipped creature deals combat damage to a player, draw a card, then you may cast a spell from your hand with mana value less than or equal to that damage without paying its mana cost. Equip {2}