To me, this is the central question of The Great Ordeal.
Why does WLW's destiny get broken by Kelmomas?
We know how WLW's destiny works in general. The Gods are timeless. Everything is one, in every respect, as Koringhus says. The Gods don't just watch out of every eye, they do so all throughout time. So Yatwer can perfectly aim WLW at Kellhus.
Similarly, it is pretty clear what saves Kellhus. Kelmomas cries out, which makes him turn, and the world suddenly takes a path not forseen by Yatwer.
But...how can that be? It isn't that Yatwer is IN the present, forseeing the future. There is no present, past or future for beings of the Outside, right? They do not "happen, all at once", as Psatma says. Whatever ends up happening, Yatwer should be seeing it even as it does so (cue WLW seeing himself ahead of and behind himself, etc).
We know that the Hundred are blind to certain entities (sentience without soul and all. They can't look out their eyes.) But how does that work, exactly?
If a Skin Spy (or other entity the Gods are blind to) kills someone, what exactly happens there, in the God's eyes? Do they just forsee the person dying with no cause? Or do they forsee them living , and then become confused when they die? That is, in the past, when the No God's soulless armies were destroying cities...did the Hundred not understand why the people were dying...or did they not even understand that they were dying ? How deep does the blindness run?
Like, if Yatwer and friends have a view of the whole timeline that is broken any time soulless entities intrude upon it...it should be gibberish by now. Populated by the time-ghosts of those who weren't supposed to have died and their descendants. So it seems like they have to be able to see at least the second order effects of the actions of things that they are blind to.
But if that's the case, then why didn't she see Kellhus reacting to Kelmomas's scream? Kellhus is reacting to something that she can't see...but she should still see him, right? I mean, his whole reign is a reaction to things she can't see. The Sranc/Inchoroi nuke is what prompted his flight to Momas, but she didn't have any trouble knowing he'd be there.
The only thing that makes sense, to me, is if Yatwer's blindness to Kelmomas (or, really, Samarmas. WLW has no trouble interacting with Thelli, so it is clearly capable of dealing with Dunyain children in the general sense) is of a different kind than her blindness to Skin Spies. But that seems absurdly contrived? Two kinds of metaphysical blind spot? No author would do that. You couldn't rely on the reader to keep track.
So I must have gone off course somewhere. Best guess remains that Samarmas muddles Kelmomas's POV enough that looking out his eyes doesn't work right, so Yatwer can account for him in a general sense (Thelli is going to his room to confront him, so WLW needs to go there...), but not in a specific, clutch situation.