Big Bang Attack

Cascade, Cascade (when you cast this spell exile
cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the
bottom of your library in a random order.
Then do it again.)

Big Bang Attack deals damage to each creature your opponents control equal to the total mana value
of other spells you have cast this turn.