Sozin's Comet

Foretell {r}{r}{r}{r}{r} (During your turn, you may
pay {2} and exile this card from your hand face down.
Cast it on a later turn for its foretell cost)
Red sources you control deal double damage. Mountains you control tap for {r}{r}.
Blue sources your opponents control deal half
damage, rounded down. Islands your opponents control don't untap unless their controller
pays {1}.