Grothama, All-Devouring is a mythic Legendary Creature — Wurm card from Bloomburrow Commander (BLC), collector number 224. Current market price: $0.63, TCGplayer market prices via Scryfall.
Other creatures have "Whenever this creature attacks, you may have it fight Grothama, All-Devouring." When Grothama leaves the battlefield, each player draws cards equal to the amount of damage dealt to Grothama this turn by sources they controlled.