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 in a random order. Then do it
again.)