We get explained that the Amiolas "weds" the soul of the one wearing it to the soul of a headstrong and self-punishing Ishroi. I suppose Sorweel's soul got "completed" in a way, making him real and thus unalterable.

Edit: ... because she can no longer see the tears in the fabric of reality that make him false.

Also: On Page 296, Sorweel is referred to as "the in-between soul that had once been Sorweel". Two pages earlier, Immiriccas's love and wrath "made him whole ".

Edit: and a little later we get the description of Sorweel sharing his memories with Immiriccas's soul, where the last but if the boy Sorweel dies in the Weeping Mountain.

They managed to rampage through Ishuäl just fine as well

I'd say that's possible. Any idea how the Absolute ties into this? He clearly demonstrates through the previous chapters that the Dunyain were wrong; But is that about the ingetoetst of the Absolute, or something else?

We get explained that the Amiolas "weds" the soul of the one wearing it to the soul of a headstrong and self-punishing Ishroi. I suppose Sorweel's soul got "completed" in a way, making him real and thus unalterable.

Edit: ... because she can no longer see the tears in the fabric of reality that make him false.

You might be right. I posted it here since the Wathi doll is explained right before the passage of the Whale Mothers, but it's a bit cross-thread. 

*Tries to summon Madness*

While rereading, I was surprised I didn't get Achamian's explanation about how the Wathi doll works and the connection (the colors in the two passages below are the match) with both the previous Aörsi chapters (about Kellhus shredding Proyas's identity) and Mimara's Judging Eye vision about the Whale Mothers and Kellhus sitting on his black throne.
I mean, the passage even starts with the vision of Nau-Cayuti meeting Shae.

A pit bent into a circle, the most perfect of the Conserving Forms...
"But isn't trapping souls an ancient art?" she asked.
"It is..." Achamian replied. He thought of the Wathi doll he once owned - and used to save himself from the Scarlet Spires when everyone, including Esmenet, had thought him dead. He had been reluctant, then, to think of the proxy that had been trapped within it. Had it suffered? Was it yet another of his multitudinous sins?
One more blemish for Mimara to glimpse with her Judging Eye?
"But souls are exceedingly complicated," he continued. "Far more so than the crude sorceries used to trap them. The intricacies of identity are always sheared away. Memory. Faculty. Character. These are cast into the pit... Only the most base urges survive in proxies."
Which was what made them such willful slaves.
"So to have your soul caught..." She trailed, frowning.
"Is to be twice-damned..." he said, trailing at the behest of a queer reluctance. Few understood the monstrosity of sorcery better than he. "To have your hungers enslaved in the World, while your thoughts are tormented in the Outside."

They seize him from time to time, the Sons of this place, and he feels the seams tear, hears his scream. But he cannot come apart - for unlike the Countless Dead, his heart beats still.
There is a head on a pole behind you.
[...]
And he sees that these things are meat, here. Love is meat, Hope is meat. Courage. Outrage. Anguish. All these things are meat - seared over fire, sucked clean of grease.
There is a head on a pole.

I also noticed a similarity between the quotes above in red, with the quotes in purple below. It's not exactly the same, but Kellhus/ the Dunyain/ TTT as an avatar of "The guy(s) bringing Hell on Earth". Stripping everything and everyone down to its bare utility, just like the "Sons of this Place" stripping down people's Thoughts (as opposed to Souls) to the bone.

Women bred into monstrous instruments of procreation, until they had become little more than puches slung about their wombs.
The misery. The huffing and moaning. The mewling screams. The inhuman men filing to their asignations, utterly heartless and insensate. The slapping of hip and genitalia. The animality of coupling stripped to its essential germ, to the milking pitch of inseminations...
Sadism without desire. Cruelty - unimaginable cruelty - absent the least will to inflict suffering.
And evil that only the Inchoroi could surpass.
And when her gaze flinches, she sees that this crim is no aberration, but rather an inevitable and extreme implication of what rules the whole. [...] The fevious pitch of intellect, domineering, devoid of compassion or humility...
And the will - the blasphemous will most of all. The deranged hunger to become God.
[...]
Suddenly she sees Him, her stepfather, Anasûrimbor Kellhus I, the Holy Aspect-Emperor, high on his throne, wreathed in darkness and fury, a malignant cancer cast across the far corners of the world...
Doom incarnate.
Suddenly she sees the Truth of the old Wizard's terror. A Dûnyain ruled the World - a Dûnyain!.

The quotes in blue also cause me to wonder if trapping souls is the way the Inchoroi made the Nonmen immortal: I mean, it would explain their damnation and why their memories fail, with Hell feasting upon them. It'd also be ironic to have the Nonmen be strung between the World and the Outside/ Hell by the Inchoroi, since they revere passages and thresholds.

On the topic of "WHAT DO YOU SEE?", there's also the one teaser about witnesses during Kellhus's sermons.

Edit: Or the topic of "Blind Cishaurim" Moe in TTT.

On a totally different note, while I'm trying to preorder the book:
Is it just me, or are there only Paperbacks available for preorder? I'm a bit annoyed by the lack of consistency in what to expect from one book to the next: All books I have are preorders, and I currently have quite the mosaic in the bookcase. It's a variation both in format and size.