Opera Masquerade

When Opera Masquerade enters the battlefield,
exile all nontoken face-up creatures face down. Starting with you, each player puts a random
card exiled this way onto the battlefield under
their control face down. Repeat this process
until all cards exiled this way have been chosen.
(They're 2/2 creatures.)
At the beginning of each player's upkeep, that
player may turn target face-down creature they
control face up.