This thought occurred to me this morning, regarding Kellhus' 'outreach program' to the nonmen. Why would he need the sorcerous might of the nonmen added to the Ordeal? I get that they're badass on another level to human sorcerers. However, he has to know that he would only find so many either 1) sane enough, or 2) willing enough to join the Ordeal. What could be their motivation to join him? Like they haven't been warring, in one way or another, for millennia anyway. Also, Kellhus has gathered the largest sorcerous might in human history.
My point is, I don't think he wants them for their power, but for their memories. Kellhus needs a guide inside the Ark, someone who's been there before, to show him where he needs to go. So, if he can get even one nonman to join the cause, what better way to access the deepest places of the Ark than to re-introduce a nonman who'd been there before? He would remember, much as Cleric did in Cil-Aujas. He could guide Kellhus, and save enormous amounts of time bumbling around in the dark, as it were.
So. Who's it gonna be? Oirunas? Or does Sorweel retain the memories of Immiricas? Or will the remnants of Ishterebinth form a cadre of sorts to infiltrate the deepest depths of the Ark?