Keurak, The Void Mirror

When you cast Keurak, each opponent reveals their hand. You choose up to 3 cards from each player's hand, exile those cards.
Keurak's power and toughness are each equal to the total power and toughness of all creatures in exile.
{7}: Choose a card in exile, if it's a spell, you may cast it without paying its mana cost. If you do, exile target permanent.