Sin, Spira's Punishment is a rare Legendary Creature — Leviathan Avatar card from Final Fantasy Promos (PFIN), collector number 242s. Current market price: — (foil $5.19), TCGplayer market prices via Scryfall.
Flying Whenever Sin enters or attacks, exile a permanent card from your graveyard at random, then create a tapped token that's a copy of that card. If the exiled card is a land card, repeat this process.