Vertixal, the cleansing fire

When Vertixal, the cleansing fire enters the battlefield, deal X damage to each creature. If a creature you control would die from this, exile it instead and put a Rebirth counter on it equal to its converted mana cost.
At the beginning of each upkeep, remove a Rebirth counter from creatures you control in exile. If Vertixal, the cleansing fire would leave the battlefield return each creature exiled by Vertixal, the cleansing fire onto the battlefield