As it turns out, even in the Ice Age, it wasn’t just Primal Fear you had to worry about.
The rape scene in The Clan of the Cave Bear. Ayla is just minding her own business when Broud happens upon her and gets the idea of ordering her to have sex with him, purely to show his dominance over her. Ayla is initially compelled to obey, but ultimately can't bring herself to submit to him out of terror and disgust. She tries to run away, prompting Broud to chase her down and brutally beat her until she's physically incapable of fighting or escaping. As if it weren't bad enough that it actually happens, it is largely told from Broud's viewpoint, leading the reader to realize just how depraved and sadistic he is. And then you remember this guy is going to be responsible for the entire clan someday. On top of all that, after the first incident, Broud rapes Ayla every day for quite a while afterward. She actually mentions he waits for her to get up in the morning so he can attack her. Meanwhile, the whole clan, including Ayla's family, just stand by and do nothing even though they can hear her cries of pain, because they believe it's Broud's right and are merely puzzled that he's showing such an interest in her. Keep in mind that that this is being done to a ten/eleven year old child.
The visions Ayla has whenever she takes the psychotropic roots considered sacred to the Clan. Not only are they frightening and incoherent, but each time she under its effects, she comes comes close to...well, it's not made entirely clear what would happen, but most characters are under the impression that if she isn't brought back in time, her spirit would be lost inside some great dark 'void', the very prospect of which is terrifying. Her first experience at the Clan Gathering is especially terrifying: not only is she under the effects of datura and an unintentionally-potent sacred drink, she stumbles upon the horrifying scene of Creb and the other mog-gurs stripping pieces of brain from the head of a man "chosen" (i.e. killed) by a Cave Bear, before ritualistically consuming them as a kind of "communion". It essentially causes her mind to snap, only halted when Creb psychically "catches" her as she's falling into the void.
The death curse, which is used by the Clan to punish severe crimes (or what they perceive as severe crimes). Essentially, anyone who has been cursed with death is considered dead by the Clan. The person is regarded not as a living person, but a lingering spirit. Acknowledging them in any way could encourage the spirit to stay and bring bad luck, so everyone will turn away and ignore the person, even if they stand and scream in their faces. They also burn all the 'dead' person's possessions. Imagine that everyone you've ever known and loved acted as though you were dead, while you're right in front of them and you can get a sense of the impact such a curse has on its victim. Most people eventually give up and die for real. And one of the scariest things about it is that this actually has some basis in reality; there are some real cultures with similar 'death curses' or shunnings that work the same way.
When Jondalar and Thonolan are attacked by a woolly rhino in The Valley of Horses. Imagine being stuck in the middle of nowhere, with your severely wounded younger brother. No one knows where you are, as far as you know there are no other people nearby who can help, and you don’t have the knowledge and materials to treat him. And on top of that, the smell of blood could attract any wild animals lurking nearby and you’re basically defenceless. Jondalar - who is still injured but in better shape than Thonolan - is left stumbling around, desperately pleading for anyone to help with little hope of being answered.
Crossing the glacier, which forms the big climax of the fourth novel. Not only is it freezing, but it’s completely barren of food and water, the ice is so sharp it can cut horses’ hooves open, if you run out of supplies you’re screwed, it takes days to cross, there’s no shelter from the elements and climbing down it can be just as dangerous as going up. And as if that weren’t bad enough, there are hidden crevices everywhere, which can open up without warning or are basically invisible until you’re right in front of them. Falling down one is almost always a death sentence...and Ayla nearly does. She’s only saved because she manages to land on a narrow ledge and has Jondalar with her to pull her up. If she’d been alone, or broken a limb, she’d be screwed.
Everything about the Three Sisters Camp. If you're a man, you'll be imprisoned, starved, beaten, denied medical attention, forced to do hard labour and be separated from your female relatives and loved ones. If you're a woman, you have to struggle to find food because your leader has forbidden you from gathering food, you're separated from your male relatives and loved ones - including any sons you might have - who are abused and used to keep you obedient. And if you're caught trying to help them, you'll be severely punished or possibly even killed. Not even children are spared, with boys being locked up in the holding pen too and essentially tortured and permanently injured if they're deemed troublesome. The leader of the camp is an utter psychopath who refuses to take any criticism and won't hesitate to harm or kill anyone who threatens (or whom she perceives as threatening) her rule. She'll either violently kill you outright or slip you poison when you're not expecting it. She's also cut you off from other camps and forbids visitors, leaving you completely isolated and without outside help. Any travellers unfortunate enough to stumble upon the camp will be taken captive and - especially if they're men - tortured and killed for the leader's sick amusement.
Balderan and his gang of psychos provide plenty of Nightmare Fuel in the sixth book, even if many of their most evil acts were committed off-page. Balderan in particular stands out as being one of the most evil characters in the series, even surpassing Broud and Attaroa in some respects; he's a Serial Rapist and budding Serial Killer who enjoys inflicting pain on innocent people. Many people who encounter him find him deeply unsettling even when he's not committing violent acts, finding that there's just something inherently wrong with him. Two incidents stand out in particular. In one Balderan and his gang kidnapped a girl and held her captive for months; it's never stated what exactly happened to her (though considering Balderan's reputation we can make some guesses) and when they finally released her, her mother states she was never the same. In another incident, he attacked a couple while they were away from their cave, killing the woman's mate in front of her when he tried to protect her, gang-raping her for hours and then stealing her supplies and leaving her for dead in the woods. When the reader first encounters Balderan, he and his gang had crept up on Ayla and were spying on her while she off relieving herself in the woods. They probably assumed she was alone and its pretty obvious what they planning on doing to her, though luckily Ayla subdues them with help from her companions.
Ayla being Called by the Earth Mother. She goes on an insane drug trip and runs blindly into a series of caves, with no torches, food or appropriate clothing. After having coming back to her senses, she's lost underground, cold, hungry and completely alone with little hope of finding her way out on her own...and, although she doesn’t realize it at the time, she’s suffering a miscarriage too, leaving her confused over all the pain and blood in an already terrifying situation.
