Sin, Spira's Punishment is a rare Legendary Creature — Leviathan Avatar card from Final Fantasy (FIN), collector number 348. Current market price: $1.38 (foil $2.81), 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.