Underworld Cerberus is a mythic Creature — Dog card from Theros (THS), collector number 208. Current market price: $0.38 (foil $0.82), TCGplayer market prices via Scryfall.
This creature can't be blocked except by three or more creatures. Cards in graveyards can't be the targets of spells or abilities. When this creature dies, exile it and each player returns all creature cards from their graveyard to their hand.