Ice Leviathan

Indestructible, hexproof, protection from blue. This creature cannot be played unless a card named Devil's Son is in a graveyard.
Pay {x}: Exile target permanents with converted mana cost X and less. As long as Ice Leviathan is on the battlefield, all permanents exiled this way remain exiled. When Ice Leviathan leaves the battlefield, return exiled permanents exiled by Ice Leviathan to the battlefield under their owners control.