Cloud of Darkness is a uncommon Legendary Creature — Avatar card from Final Fantasy (FIN), collector number 481. Current market price: $0.85 (foil $9.42), TCGplayer market prices via Scryfall.
Flying Particle Beam — When Cloud of Darkness enters, target creature an opponent controls gets -X/-X until end of turn, where X is the number of permanent cards in your graveyard.