Just because he claims that he's Lucian's son doesn't make it so. Until there's proof or explanation of it, I see no reason to believe that he is who he says or thinks he is. It just doesn't fit.
The end of Act 1 took me by surprise too, though. Considering Alexandar seems like a big deal, I kinda expect him to show up again, at least in some capacity. Death doesn't necessarily have to write you out of the story.
