Demonfire is a uncommon Sorcery card from Ravnica Remastered (RVR), collector number 107. Current market price: $0.28 (foil $0.31), TCGplayer market prices via Scryfall.
Demonfire deals X damage to any target. If a creature dealt damage this way would die this turn, exile it instead. Hellbent — If you have no cards in hand, this spell can't be countered and the damage can't be prevented.