Caven, Underworld Thief

When Caven, Underworld Thief enters the battlefield exile the top three cards of each players library.
Whenever Caven, Underworld Thief attacks, he
gets +X/+O for the highest converted mana cost
of a card that's in exile.
Whenever Caven, Underworld Thief deals combat damage to a player you may cast target card that player has in exile without paying its mana cost.