Hellfire Mongrel is a uncommon Creature — Elemental Dog card from Duel Decks: Ajani vs. Nicol Bolas (DDH), collector number 48. Current market price: $0.30, TCGplayer market prices via Scryfall.
At the beginning of each opponent's upkeep, if that player has two or fewer cards in hand, this creature deals 2 damage to that player.