... not Moenghus, not Cnaiur or some soul mash-up of the two. He was, as he states, a survivor of the sorcerous battle in Shimeh and took the name of the cant that led to his family's death.
Madness has convinced me that he is "the boy" from the end of TTT. And if so, it seems pretty likely that he's also a tool of the Consult. Perhaps unwittingly, but a tool just the same.
Given that he seems to be alive after the confrontation in Fanayal's tent, it seems likely that Kellhus has a use for him. But what is it/
My crackpot is that Kellhus will somehow use him as a tool against the no-God. Maybe he'll mind-fuck Meppa into a emotional tornado, line him up in front of the Sarcophagus and let him unleash the Water?