This is kind of a catch-all speculation post regarding Kellhus and his limits (or lack thereof). I'm going to wander around some topics, but please feel free to insert more if you're so inclined. Some of these will have been touched on before, but I'm trying to get an overall baseline for what people think Kellhus is actually capable of, and what he is not. Some points to start:
1) Teleportation: It's been accepted as doctrine that a metagnostic sorcerer can teleport the distance of horizon to horizon, or distances relative to that which they can reasonably see. While this may be true of world-born sorcerers (and half-Dunyain for that matter), I'm not so sure it applies to Kellhus himself, being full Dunyain. Leaving the underground Mansion after knifing Moenghus, he obviously couldn't 'see' Shimeh, yet he popped into the sky above it, assumedly straight from that underground room. With his mental faculties, he could easily have studied the landscape and held that target in his mind for probably an indefinite period of time, thus negating the need to see his destination. Likewise, twenty years later, he's supposedly making many jumps from the location of the Great Ordeal back to Momemn, and he plays like he's tired because of it. He may very well be tired, but I don't think he's actually making the same jumps others would. I think he's tired because it's more arduous to teleport to someplace you can't directly see. I think he made one jump, straight from the Ordeal and into the throne room on the Adiamine Heights, but it was taxing even for him. On a tangent, but directly related to this subject, back when Sasheoka was assassinated by the Cishaurim, thus sparking the war between the Scarlet Spires and the snakeheads, I think it was Eleazaras who related that the Cishaurim simply popped into view in their deepest, most secure sanctum. So, the Cish not only had the ability to teleport, but to teleport to someplace they couldn't see directly. This, to me, is evidence that Moenghus had the knowledge, if not the power, on how to accomplish this feat. Maybe the fact that they're blind actually helped them, as they can't really 'see' in the traditional sense anyway. Just food for thought.
2) Meta-Daimos: This has been brought up in another thread as a possibility. I think it's an inevitability. If Iyokus can summon and control three Ciphrang at once, surely Kellhus can up the ante exponentially. I would imagine he could field a small army of Ciphrang, and most likely control them to a much greater degree. And/or he could probably yoke more powerful demons. Imagine behemoths the likes of which no one has ever been able to control before, powers out of reach of world-born men and their frailties. And Kellhus, imo, is not deterred by fears of damnation or eternal torment. He's gone all-in and intends to come out on top. Might be his ace-in-the-hole in the war: an army that doesn't need to be marched anywhere, just summoned when you got there.
3) Meta-Compulsions: So, if compulsions are indistinguishable from one's own thoughts, and with Kel's advanced conditioning taken into account, would he not just be able to outright re-write someone's psyche to become whatever he wants them to be? When Esmenet was possessed by Aurang (Aurax? sorry, can never remember which is which), Kellhus was able to suppress some of those experiences in her (am I remembering that right?) Regardless, I believe his compulsions could, in theory, become a tool by which he could dominate/enslave/compel virtually anyone. Isn't this essentially what the Whelming is? Couple this with dream communication. Moenghus was able to communicate via dream, even though he was supposedly weak in the water, all the way to Ishual. Kellhus would have been easily more adept at this kind of thing. My postulation, in this instance, is that he could have dream-contacted the people he knew before he left and put the whammy on them (scientific term here). In this scenario, once he had them firmly under his control, he may have used them the purge the rest of the Dunyain, leaving only those loyal to him left. Then he shows up, completes their whelming, destroys Ishual and inserts his slaves into his army. Others have postulated that there may be full Dunyain under Kel's control. Not my idea, but if that were true, maybe this is how he did it.
Okay, I'm losing steam. There may have been other specifics I had in mind, but I can't remember them if there were. What do you think? Bullshit? Something? Would love to hear what anyone else might think about any of this.