Aurel, Portal of Conduits

{t}: Add {c} to your mana pool.
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card whose converted mana cost is less than this spell's converted mana cost. You may cast that card without paying its mana cost. Then put all cards exiled this way that weren't cast on the bottom of your library in a random order.)