Voices from Beyond

When Voices from Beyond enters the battlefield, search your library for up to five nonland cards and exile them face down. Then shuffle your library.
For as long as those cards remain exiled, you
may look at them, and each card has limbo.
The limbo cost is equal to its mana cost. (You
may exile cards with limbo from your hand for its limbo cost at any time. You may return it from exile
to your hand anytime for its limbo cost.)