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

Aagrail only recognized Ra'ilag in the "Warlord" video after Ra'ilag himself told him, and before that, Kha-Belekh addressed him as a stranger.

This could have been a grievance like "You betrayed me, from now on you are nothing to me," and the statement that "Yes, I am Aagrail!" (I am, of course, slightly exaggerating) could have been perceived as "not all is lost, maybe I can bring him back to my side." Another argument in favor of the fact that Kha knew Ra'ilag's identity is that he immediately sent Biaru to him.