Maelstrom

{t}: Add {u}. Exile the top card of your library.
{x},{t}: Return a card with converted mana cost X
that was exiled this way to the battlefield under
your control.
{t}, Sacrifice Maelstrom: Return all cards exiled
with it to the battlefield under your control.
Whenever a nonpermanent would be put on the battlefield, exile it. You may play it without
paying its mana cost.