Ghaltahalpetalimoc

This spell costs {x} less to cast, where X is the total power of creatures you control.
Flying, double strike, vigilance, trample, indestructible, deathtouch
This spell can’t be countered.
Whenever an opponent casts a noncreature spell, exile the top card of each player’s library, then you may cast any number of spells from among those cards without paying their mana costs.
When Ghaltahalpetalimoc enters, destroy each creature your opponents control.