Buster Sword is a mythic Artifact — Equipment card from Final Fantasy (FIN), collector number 255. Current market price: $47.35 (foil $64.11), 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}