Invoke the Titans

Foretell {w}{u}: Exile this card from your hand
with a prophecy counter on it: You gain 2 life
(You may cast this card from exile if it has a prophecy counter on it. Foretell only as a sorcery.)
As long as Invoke the Titans is in exile, Giant creature spells you cast cost {1} less to cast.
Giant creatures you control get +2/+2 and have vigilance.