Aurelian Sol, the Star Forger

Flying
Whenever you cast an instant or sorcery, put a
-X/-X counter on target creature an opponent
controls, where X equals that spell's mana cost.
If a creature dies this way, put a Stardust counter
on Aurelian Sol the Star Forger.
Remove all Stardust counters {t}: deal X damage
to all creatures you don't control, where X is the
number of Stardust counters removed.