The full opening cinematic was shown last night at the VGA awards. We see the Heavenly Host fighting with the armies of the Burning Hells in a prophetic vision from Leah. She awakens to hear Cain speaking of the terrible events that are going to happen.
From the night sky meteors rain down on the land, destroying the Cathedral where Cain and Leah reside and opening the crater for the armies of Hell. Cain was caught by the impact and vanished into the crater, leaving her behind, alone with the fate of the world at stake. 
Transcript:
Cain: And at the end of days… The first sign shall appear in the Heavens. Justice shall fall upon the world of men.
Cain: The armies of Light and Shadow will clash across the fields of eternity.
Leah: [Startled]
Cain: Leah are you alright my girl.
Leah: It was nothing, uncle. Just… a bad dream. We should be getting home.
Cain: But there’s still work to be done. If these translations are correct, [Coughing] the powers of hell could already be on the move.
Cain: The world must be told of the coming darkness. You do believe me, don’t you Leah?
Cain: It has begun.
Leah: Leave it uncle, it’s not important.
Leah: [Shouting] UNCLE!
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