When the party talked to Isani, she mentioned Demisiosa as a person that, like Folduin Caerlinn, were merely a tool she used as a mean to reclaim her divinity from the false gods.
As the party ventured through Farhold Keep, they saw several Farwalkers being taken over by a powerful psionic force that spoke in a draconic voice to them, taunting them of their impending failure. The party also saw flashes of a draconic creature in clusters of sapphires underneath the keep, and heard the large roars coming from deeper within the underground lair.