Stormbreath Dragon is a mythic Creature — Dragon card from Theros (THS), collector number 143. Current market price: $0.59 (foil $6.33), TCGplayer market prices via Scryfall.
Flying, haste, protection from white {5}{R}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.) When this creature becomes monstrous, it deals damage to each opponent equal to the number of cards in that player's hand.