Leyline Tyrant is a mythic Creature — Dragon card from Tarkir: Dragonstorm Commander (TDC), collector number 221. Current market price: $2.14, TCGplayer market prices via Scryfall.
Flying You don't lose unspent red mana as steps and phases end. When this creature dies, you may pay any amount of {R}. When you do, it deals that much damage to any target.