Egg of Sirens

Hideaway (This creature enters the battlefield tapped. When it does, look at the top four cards of your library, exile one face down, then put the rest on the bottom of your library.)
Pay 2 experience counters: Randomly choose a face down card you own in exile and manifest it.
Whenever a player attacks, exile Egg of Sirens then return it to the battlefield. Untap it. Then, you get an experience counter.