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.)