Zhulodok, Void Gorger

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.)