Xardas and Beliar

Im currently replaying Gothic 2 for the like 10th time and this time something really struck me while playing through the story. In Chapter 3 when you have to repair the eye of Innos during the ritual with Pyrokar, Xardas and Vatras, Pyrokar says he wont go there because of xardas. Now youre fighing against Beliars forces (dragons, Sleeper etc.) but Xardas is on the same side as Beliar. How does that make any sense to fight against Beliar all the time and then work with someone whos literally working for your biggest enemy?