Have you watched the Age of War Trailer?
My understanding is that in Chapter 2 or 3 of the Age of War, the treasure hoards players have been building up will become targets for the invading Stygian Army, in Purge-like attacks.
Also, the Ruins of Al-Merayah are gone, and apparently this is where the Stygian Army will be setting up a Base. This base will be part of a new game mechanic, a Siege on an NPC Base.