Stormchurner Dragon

Flying
Whenever a player casts or copies a spell, put a
storm counter on Stormchurner Dragon.
At the beginning of each end step, remove all
storm counters from Stormchurner and deal X
damage to any target where X is the number of
storm counters removed this turn. If X is 10 or greater, deal that much damage to each other
player and creature instead.