Xizor was a waste of a character, really. It's been a while since I read "Shadows.." but from what I remember, Xizor's main ambition was to make Vader look like a fool so that he could be the Emperor's second in command. Why go to all that effort to be someone's lackey? Why not have ambitions to overthrow the Emperor? It was entertaining enough to get me through the book, but was completely illogical. Thrawn may have been annoying at times and the Ysalmiri (sp?) were a stretch for me, but at least Thrawn was a badass. Not a waste like Xizor.