How is Dark Messiah connected to Heroes of Might and Magic?

Exactly, he was altered by Urgash's magic, but he isn't a full-fledged demon. As for the exiled Wood Elves, when Malassa's magic touched them, it didn't turn them into Faceless Ones. Regarding their personalities, Biara and Xana are similar; they are both succubi and schemers. Kha-Beleth's appearance in Heroes of Might and Magic V and Messiah is also different, and we haven't seen Biara in human form; we've only seen her as Beatrice and Isabelle.

Well, all succubi have similar personalities, but they are still different. Xana loved Sareth very devotedly; she didn't even care which side he chose. But Biara... well, she couldn't love devotedly. She has a more rigid, more self-centered personality, I guess. No, their personalities are different. And their appearance too - Xana in her demonic form is the same as in her human form, only with horns and without clothes. Biara, on the other hand, changes drastically; she has red skin, a bald head with TWO, not SIX, horns like Xana.
As for the fact that Railag couldn't become a Demon Lord... Nonsense! He commanded them, was the right hand of his master, and the demons obeyed him. Judging by the game, they didn't care whether he was a full-fledged demon or not; the main thing was that he was in demonic armor and fought for them. So, if he had become a Demon Lord, the same thing would have happened - all his subordinates would have deeply not cared about his origin.:smile17: