C'thulu, The Great Old One

Colorless spells you cast from your
hand with mana value 7 or greater have
"Cascade, cascade." (When you cast one,
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.)