I think you could change certain aspects though, beyond fluff. The problem with having this class, I feel, is that it makes the "choice" of becoming a Lich valid for basically any caster. Rather than being a unique manifestation of a caster that has gone beyond the bounds of mortality set by the gods themselves it becomes something you would almost expect a high level wizard to do.


Off the top of my head I would say exchange paralysis, a fairly terrible way to kill even an evil character, with Gaes or teleport. Maybe even connect them to the place they are protecting or require them to give up part of their personality, or limit their behavior in some way.

But you are much better at this than I, so take these as you will.