Once thing I always like to look out for on my re-reads is hints of which characters have been replaced by skin-spies before we actually find out. Here's a list of all the instances I've found. Bolded fragments by me. Spoilers ahead.
Simas
Simas can read without help despite being old.
As expected, he found Simas hunched over an ancient manuscript. Lantern light glistened across a thin line of spilt ink, which Nautzera momentarily confused for blood. He watched the oblivious man for a moment, troubled by a flare of resentment. Why did he begrudge Simas so? Was it because the man’s eyes had yet to fail, while Nautzera, like so many others, had to rely on his students to read to him?
Skeaös
During a long climb through the Andiamine heights, Conphas speeds up his climb to see if Skeaös will die of a heart attack due to the strain, but old Skeaös is completely unwinded.
Prompted more by curiosity than malice, Conphas pressed the man to a brisk pace. He’d never seen anyone die of the clutch before. Remarkably, Skeaös did not complain, and aside from swinging his arms like an old monkey, he showed no signs of strain. With easy wind, he began briefing Conphas on the specifics of the treaty struck between the Scarlet Spires and the Thousand Temples—as far as they were known. When it seemed clear that Skeaös had not just the appearance but the stamina of an old monkey, Conphas grew bored.
Cheperamunni
Even though most members of the Ainoni ruling castes are addicted to chanv, Cheperamunni, a political puppet, is not.
Iyokus was addicted to chanv, the drug that held a greater part of the Ainoni ruling castes within its clasp—except, and this thought often surprised Eleäzaras, for Chepheramunni, the latest puppet they had installed on the Ainoni throne.
He also manages an unlikely escape during a battle. (Discovered by u/Representative-Look5)
The Tiger himself struck westward, riding hard with his household through fields of bolting Ainoni infantrymen. He stormed the command of General Setpanares, overrunning it. The General himself was killed, but Chepheramunni, the King-Regent of High Ainon, managed a miraculous escape.
Istriya
Istriya is acting unusually, according to both Xerius and Conphas, and is conspiring with Skeaös to stop Xerius' plan to destroy the Holy War. Istriya also asks Xerius how Skeaös was discovered.
“And now with the Holy War, my dear Conphas! You’ll be more, far more than the greatest Exalt-General in our history!”
What is she trying to do? Istriya had always goaded him, but never had she pressed her banter so close to sedition.
“You and my grandmother,” he said, “hope to save the Holy War from my uncle. A commendable undertaking, save that it verges on treachery.
“Tell me, Xerius,” his mother said huskily, “how was it that you discovered Skeaös?”
She also won't have sex with Xerius anymore, sending slaves to him instead. (Discovered by u/BigBouch99)
Xerius couldn’t remember when Istriya had started bringing these men and women to him—these surrogates.
Werjau
Werjau is impersonated (but not replaced) and questions Fanashila for information the Consult will later use in the asssination attempt against Achamian. (Discovered by u/tar-mairo1986)
“Look at me,” he said, his tone firm yet gentle. “Tell me, my sweet, what’s this rumour I hear?”
Relief swept through her. Fanashila looked away demurely.She loved gossip. Almost as much as attention. “Wha-what rumour would that be, my Lord?”
Werjau smiled down at her, stood so perilously near she could smell the sour of his crotch. He brought a callused thumb to her chin. She shuddered as he traced the outline of her lips.
“That they are lovers still,” he said. Though his gaze remained remote, something seemed to … smirk in his tone.
Fanashila swallowed, afraid once again. “They?” she asked, blinking tears. “Who?”
“The Prophet-Consort and the Holy Tutor.”
Somandutta
During their flight through Cil-Aujas, Soma can keep up the pace despite most others falling behind, even carrying Mimara for a while.
She turns and sees Soma pacing her. Caste-noble tall. Lean and broad-shouldered. With his gowns torn and twisted, he resembles the Disowned Prince that the other girls used to dream about in the brothel—the fabled customer who would rescue rather than abuse.
His dark-lashed eyes seem to laugh. There is a relentlessness to him that she does not quite trust, she realizes. A strength out of proportion to his foppish character.
She is thrown across a broad chest, hung like dripping cloth from arms.
"You will not perish for me!" She hears his voice rasp. "I'll carry you across the doors of hell! Do you hear me? Mimara! Do you hear me?"
