User blog comment:Metadwarfosis/In anticipation of volume 11- Dwarven Kingdom and Expectations/@comment-178.175.66.8-20160813130218/@comment-29248623-20160813153245

The Doppelganger might also serve as a substitute for Ainz, something like a personal visit with the dramatic shock factor of the Sorcerer King's presence but that "Kill Jaldabaoth plan" also works.

It's more likely that the one PDL mentions is a hibernating dragonlord but your (Grimraven) idea is much more interesting. An NPC would be more likely over a player in my perspective.