The Plane of Hypnerotomachia is a different dimension, or universe, or something. If Damian or Ygerna don't have some kind of power or control there, they they have the services of someone or are in possession of something that does. This plane is not mentioned in Beyond Divinity, though that game does contain a bit of info on other realms reachable by rifts.
Just after posting this topic, I started FoV; the I saw the Hypnerotomachia sword that I bought from Deodatus in the main game. Its description and Berhrlihn comment about the dimension (I'm afraid the translation is not very fortunate) gave me the clues to your explanation ^_^ Thanks anyway. I'm not sure why, but I was sure that this had something to do with Beyond Divinity.
In Ygerna's memory you are fighting her memory of Zandalor and the Divine.
Yeah, I know; but before the ending, just the moment you enter the memory and talk to the poeple there... well, I liked the idea of a greater machiavellian plot by Ygerna and Damian
