These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Aurang and Aurax are the twin princes of the alien race, the Inchoroi. After crash-landing during the height of the mystical Cunuroi civilization, a war broke out between the species. Aurang and Aurax were the only survivors of the Inchoroi and engineered a plague that killed every female member of the Cunuroi and made the males immortal so they'd suffer forever. They also helped create the Sranc, hideous creatures whose existence is simply pain and lust so that the only way they interact with other beings are killing and raping them. To prevent their own damnation for their sins, the two plan to fill Hell with so many souls, the door will be shut permanently. For this end, Aurang and Aurax mastermind hundreds of horrible murders, engineer genocidal wars for their own ends, and created a being called the No-God that killed every baby to be born for a decade. Aurang and Aurax are also sexual sadists who are fond of rape as an interrogation method. Aurax in particular enjoys raping a victim's wife in front of him before giving her and said victim's family to the Sranc long after it is clear none of them have the answers Aurax wants.
Epileptic Trees: Fan theories on the nature of the No-God can sometimes veer towards this, as well as many about Kellhus.
Foe Yay: Between Cnaiur and Kellhus and as well Cnaiur and Moenghus..
Ho Yay: Moenghus and Cnaiur, which resulted in Cnaiur killing his father. This is the reason why there is latent Ho Yay between the adult Cnaiur and Kellhus, even though it's more like Foe Yay.
Magnificent Bastard: Kellhus. He is biologically human, but mentally and ethically an alien without emotion. To assume control of the Holy War and make entire nations follow him, he decides to do it through religion. Kellhus slowly transforms their entire religion with himself as the Jesus Christ figure.
Marty Stu: Kellhus can come across this way because he's The Ace to a superhuman degree, but he's also an Anti-Hero with in-story justification for his abilities, which come at the price of his humanity.
Seswatha's memories of the Apocalypse are literallyNightmare Fuel. The Mandate sorcerers dream it every night so they can never forget what it is they fight against. For example, Achamian once dreams of the fall of the city Sauglish. Grown men are dashing their babies' skulls against the street so the Sranc can't rape them to death and then rape the corpses. The Apocalypse is thirty-two years of Tear Jerker: Achamian virtually never refers to it without calling it "heartbreaking." Oh, and the No-God? His very existence is such that babies can't be born alive if he is. The eleven years of the No-God's existence were called "the Years of the Crib" because all babies were stillborn.
The epilogue of the second book, where the Inchoroi appear onstage, is the single most horrendous scene in this whole series, and that says a lot.
The experiments of the Dunyain upon human captives. To learn how to manipulate people by reading their facial expressions, their young are taught "neuropuncture". In this process, living captives are strapped down and their faces dissected, so teenagers can experiment with their facial muscles. While they're still conscious.
The black halls of Cil-Aujas.
The view of damnation in the afterlife that we get from Mimara's Judging Eye in The White Luck Warrior.
Shae÷nanra's backstory. Also, his present physical form.
The Inchoroi are a self-described "race of lovers", wholly obsessed with sexuality, sexual violence, and rape of all sorts. And it only gets worse from there on. As a reviewer aptly put it: "Scott Bakker's books are not dark and gritty. They're pitch-black and sticky."
Incest between Emperor Xerius and his mother — especially when she gets a teenage sex slave for him, and Xerius makes his mom stay and teach the girl how to "properly pleasure" him.
A scene where the Mother-Supreme of Yatwer's cult smears blood from her period in the faces of male worshipers, "a red line of hatred", after having sex with them.
Tear Jerker: Many examples. This is probably the most depressing well-known fantasy series.
Achamian is tortured by the Scarlet Spires. His best friend Xinemus, a religious man who is conflicted about his friendship with a "blasphemer", comes to the rescue. But the Scarlet Spires subdue him and torture him as well along with Achamian, gouging out his eyes. When Achamian escapes and finally returns to the war camp, Esmenet (the woman he loves) has left him for Kellhus. The saddest part was that she had sold herself into sexual slavery to return to Achamian in the first place.
The scene where the little orphan boys watch Maithanet's procession through the streets. It's depressing because one of them prostitutes himself because he's too scared to steal, and because orphans are not considered "real children". The scene ends with that boy being taken away by a slave trader.
Cleric and his fate. Achamian was forced to kill him, because Cleric (who was insane from amnesia) loved him and Mimara to the point where he tried to kill them, in order to remember them.
Kellhus' Great Ordeal starts running into this. The Ketyai of the South, seventy thousand strong and led by King Umrapathur II of Nilnamesh, are totally annihilated by the Sranc Horde and by attacking Bashrag, while the Grandmaster of the Vokalati goes insane and starts killing both soldiers and Sranc with his sorcery. The Grandmaster of the Mandate then has to kill him, causing a battle between the Mandati and the Vokalati even while tens of thousands of soldiers are being raped to death by the Sranc below. Umrapathur dies praying that the Great Ordeal will survive him, even as the Sranc begin violating him. When Kellhus finally arrives to rescue them, the sorcerers have survived but only "scant hundreds" of the soldiers on the ground still live. Holy shit.
Uncanny Valley: Like all Nonmen, he is tall and superhumanly beautiful, with marble-white skin. But there's something very "off" about him, which all characters note. His teeth are fused, his face has the same features as a Sranc, and his voice has the "tones of a deformed child woven into it."