Kar'niss sounds like he would be insanely powerful as a controlled undead.
I've never tried to use the Shadow Curse to make undead.
I wonder if it's possible to turn Z'rell or the Warden into undead? Although they're probably too high level to be able to control. I wouldn't expect to hit level ten until after defeating them.
The strange ox? Could we somehow force the strange ox into becoming an undead variant within the shadow curse?
