I guess that Ygerna hooked herself into the Dragon Slayer's brain shortly after Talanas vision of the flying fortresses ended.

I suppose that the only consolation for the ending is that at least now Zandalor might realize that something is wrong once he realizes that Ygerna is alive and so is Damian.

The next game Zandalor will will probably say to the designated hero something like "OK, NEW plan... kill Ygerna to weaken Damian, then kill Damian."

They could call the next game:

Divinity 3: Unus magis vicis (One more time)
Divinity 3: Permissum nos Tendo Is Iterum (Let's Try This Again)

or my favorite:

Divinity 3: Maybe The Divine Should Have Murdered That Baby After All