Inferno of the Star Mounts is a mythic Legendary Creature — Dragon card from Secret Lair Drop (SLD), collector number 1015. Current market price: — (foil $7.64), TCGplayer market prices via Scryfall.
This spell can't be countered. Flying, haste {R}: Inferno of the Star Mounts gets +1/+0 until end of turn. When its power becomes 20 this way, it deals 20 damage to any target.