Smokemage

Flash
When Smokemage enters the battlefield, you
may pay {x}. If you do, exile it and X other target
creatures you control in a face-down pile, shuffle
that pile, then manifest all cards in that pile. (To manifest a card, put it onto the battlefield face down
as a 2/2 creature. Turn it face up any time for its
mana cost if it's a creature card.)
"Now you see us, now you don't."