Circe, First Deviant

You may cast any card as a face-down 2/2
creature for {3}. Turn it face up any time
for its mana cost.
Whenever a face-down creature enters the battlefield under your control, draw a card.
Whenever a creature is turned face-up, you may
exile the top card of target opponent's library.
You may cast that card as a face-down creature.

"Wanna take a peek?"—Circe