Master of the Inward Sun

Whenever you cast an instant or sorcery spell, put a +1/+1 counter on Master of the Inward Sun. Then, if that's the third spell you've cast this turn, remove all +1/+1 counters from it and it deals that much damage to each tapped creature.
Do not strike the first blow. But if you strike the second, ensure there will not be a third.