WARNING: Unmarked spoilers below.
- The Abyss is a nightmarish dimension outside of time and space inhabited by bizarre, near-universally hostile creatures called Chains (which are essentially demons) that can't be killed by conventional means. The only beings that can safely enter the Abyss are Chains and the Baskervilles.
- If a person is somehow able to escape from the Abyss, that doesn't guarantee they'll be okay. Since the Abyss exists outside time, they could exit anywhere in the past or future.
The Mutation of Sablier
- Due to the Tragedy that happened a century prior to the story, Sablier is now an Eldritch Location in its own right. The closer one gets to the hole, the more they are exposed to the Abyss' power. The people get lured in by echos of the past and become lost. Their bodies become warped by the power of the Abyss without turning into chains, being brought into a zombie-like state instead.
- As we have already said, Chains are for all intents and purposes this series' equivalent of demons. Let's solidify this comparison further, shall we ? Since Chains can't stay outside the Abyss on their own, they form contracts with humans by claiming if enough lives are sacrificed, history can be changed.
- Although their myriad of grotesque appearances do make most Chains terrifying, what they do to people who make contracts with them certainly helps. See, to make a contract with a Chain, one must take some of its blood. Legal contractors take it within a small mirror they keep with them at all times. Illegal contractors, however, directly ingest said blood. That's where the trouble starts. The thing is, after the contract is formed, a mark known as an Incuse forms on the contractor's body. The Incuse is shaped like a clock, and like a clock it measures time : the time left to the contractor. Unless the Chain is killed, the hand of the Incuse moves inexorably, and once it makes a complete turn, the unfortunate contractor get cast into the Abyss, where they either get eaten alive by Chains or end up becoming one themselves.
- The Cheshire Cat: While he isn't much of a front-line combatant, he is easily one of the more dangerous Chains. Unlike other Chains, who need a contractor to leave the Abyss, he can freely traverse between dimensions. If attacked, he can dissolve into a black mist to avoid harm. He can trap people in his pocket dimension where their own memories are used against them. Should the fight go bad, he can always flee with his dimension hopping abilities, collapsing his pocket dimension behind him, leaving those trapped to die in an empty void.
- Duldee: In most media, mind control can be fought off with a good "I Know You're in There Somewhere" Fight. Not here. Duldee gains more control the more the victim fights, making any attempt of the victim to struggle free futile. Oh, and her contractor isn't completely exempt from her influence.
- The Bloody Black Rabbit/B-Rabbit: The most powerful chain in existence, the B-Rabbit has the power to destroy the world. Not by blowing it up, but by destroying what keeps the Abyss out. It wields a scythe and a floating Variable-Length Chain as weapons and its power reduces everything, even other Chains, to dust.
- Humpty Dumpty: It can contract with multiple individuals at the same time, allowing it to prolong the contract, it manipulates its contractors' memories constantly, and it has a taste for cutting off heads.
- The Mad Baby in Retrace III, which takes on Sharon's appearance. When Oz notices something's wrong, it turns, showing several bulging eyeball protruding from Sharon's face.
The Intention of the Abyss
- The Intention is a massive Mood-Swinger, going from mad, to crying, all within a few minutes at the slightest provocation.
- Her alternate form is a limbless white rabbit doll in a dress with black, bleeding pits for eyes.
- She casually plucked out Break's left eye with her bare hands simply because she thought his eyes were pretty and she wanted them. She was going to take the other one as well, but got distracted.
- Oh, and she licked the blood off of it. Yeah.
- Every Child of Ill Omen has occasionally shown extremely unstable and perhaps even psychotic behavior. However, this is probably due to the fact that they have all been heavily traumatized by other people and situations, often because they're Children of Ill Omen, rather than something genetic.
- When she was younger, Lacie danced under blood rain and acted Cute and Psycho. However, as she got older she matured significantly, and this aspect of her personality faded away. Besides simply maturing, this is likely also because of her rapidly approaching imminent fate as she ages.
- Vincent still shows plenty of his childhood issues. As a kid, he had the habit of cutting things up with scissors (cats are NOT immune), and as an adult he cuts up dolls, animals, and people...often while displaying sweetness and politeness the entire way.
- Break is usually a sweet-craving troll who appears and disappears out of freakin' nowhere. Unless you're his enemy or an Unwitting Pawn. If you're the latter, then he'll be as manipulative as possible to make his plans go well (and he'll even tell you that he's only using you). If you're the former, then he'll gladly fight you, torture you AND make some frightening expressions. His silly behavior's still around though.
- And in times of extreme distress he will scratch at his empty eye socket, causing it to bleed. He's also going blind in his remaining eye.
- The entire family is under the command of a single individual who has the authority to order the deaths of everyone in an entire city, no questions asked. Oh, and each member commands a small Eldritch Abomination.
- Becoming Glen doesn't seem to be a happy fate. When you're "lucky" enough to live long enough without getting killed, you will still have to deal with your body deteriorating from the strain of having too much power of the Abyss in you. Once transferring Glen's soul to the next vessel is done with, you will gradually start dying a slow and painful death, and eventually turn into a chain. It's remarkable how Levi never stopped smiling throughout the ordeal, except for the occasional moments of shock.
- Then, there's also the chance that you will end up having a Child of Ill Omen for a sibling, whom you will have to send into the Abyss to be killed Deader Than Dead.The Worse part is that everything about the Children of Ill Omen were lies by the Jurors as they were a thereat to their plans being irregulars created by the cores basically all the Baskervilles were just tools for their stories and they were sacrificing innocent people for nothing.
- Even without that, you will end up distorting reality around you, especially the lives of those around you, and being Glen amplifies this. Just ask Leo. Or, well, any of the Glens, really.
- How about Oswald's plan? He wants to go back into the past and kill his OWN SISTER, someone he cares about dearly.
- Whenever Oz has a Freak Out!, things quickly become violent and disturbing.
- In Cheshire's dimension, Oz comes across the illusion of Alice's dead body, triggering Oz. Through unknown means (at the time), he begins to destroy the dimension. In a dazed state he declares that he will kill everything and everyone who makes Alice sad. When he hears Alice say that she's scared of herself, he decides that he would kill Alice without hesitation.
- This image of Oz being soaked in blood with the revelation of him being B-rabbit. It is incredibly disturbing.
- Oz was B-rabbit once upon a time, right? He must've been a total psycho who loved killing. Nope. The entire time Jack orders him to kill people, you can hear Oz shouting, "No, I don't want to kill people!" Then, when Jack runs into Alice, she gets completely stiff and asks him what he's done to Oz. She says, "Can't you see Oz screaming through his tears?" Then you get this image: Sweet dreams.
- Jack's obsession with Lacie outright borders on psychotic, what with wanting to send the world Lacie loved into the Abyss just so she wouldn't have to be lonely in the Abyss anymore. Then, there's his treatment towards Oz...
- Normally yanderes visibly go nuts when their loved one is threatened, and the madness stays with them. Alternatively, sociopaths are extremely good at faking emotion and acting friendly but go a little deeper and they simply don't care . Jack is neither. He is completely, utterly rational and reasonable in his actions regarding Lacie even when they're obviously insane and he never shows anything other than a genuine smile even when he's planning something incredibly twisted. He is a Dogged Nice Guy taken to the extreme and gets creepier when you think about it. The fact that he creeps out a Baskerville should clue you in about how disturbing this guy is.
- Jack's fate after the Tragedy. Reduced to fragments of his soul desperately holding on to life, de-aging back to a baby and then returning to his former age without really knowing what was happening, several times. All the while never being completely sure that he would still exist after this cycle.
- The more obvious it becomes that Jack is not outright evil or yandere-ish but empty, the more unnerving his character gets. His confession during the last volume that he's obsessed with Lacie not because he loves her but because he hates her, as well as that extreme resentment is the only thing that successfully allows him to feel alive, is absolutely bone-chilling.
- One of Jack's most disturbing moments isn't even fleshed out. Although we never find out exactly what he told Arthur, the fairy tale he once heard about an "empty man" that he decides to tell Arthur is quite obviously his own story. Arthur, who was infatuated with Jack, fears him for the first time after realizing the truth about the "fairy tale" Jack told him.
- There's a nightmare-inducing scene in the first volume. Oz falls into a hole and finds a mysterious grave, and then he starts hearing a strange music-box tune that he recognizes in his heart, even though he swears he's never heard it before. Then he starts to hallucinate (although this "hallucination" is actually in all likelihood a distorted flashback due to being in Jack's body) and ends up in a room full of extremely unnerving dolls who are speaking and telling him nonsensical things like "she's going to be so happy" and "she's been waiting for you." Then a disturbing young girl with hair over her eyes and a white dress comes and tells him she's been waiting for him for many years and that's she's so happy to finally see him again. Oz, obviously having no idea what's happening, asks what and who she is, and she goes berserk. Her eyes turn into empty, bloody sockets and she tries to strangle him, telling him that she will never forgive him for forgetting about her and that no matter where he runs, she will always find him.
- To top it off, Oz says that even after the hallucination ended, he could still feel the sensation of being strangled.
- There is an explanation for this scene, but it's only revealed many, many volumes later, and it's not even revealed directly—the readers have to infer by themselves. The fact that both the readers and Oz are forced to go for an incredibly long time without having any idea what this scene is supposed to represent makes it even more unnerving.
- To top it off, Oz says that even after the hallucination ended, he could still feel the sensation of being strangled.
- The incident in Sablier that happened shortly after Leo became Elliot's servant. When your new and Only Friend gets stabbed by an Eldritch Abomination right in front of you and ends up being contracted to it to stay alive, you'd definitely wish it was all a nightmare.
- This panel of Lily after being shot in the head and surviving.
- This is the real me... ♥
- Also doubles as a twisted Funny Moment. Vincent's face is priceless.
- The Tragedy of Sablier. It's a massacre, after all. And said massacre happened to double as a Mercy Kill to save the people within Sablier from a Fate Worse than Death, as Sablier starts to fall into the Abyss. Poor Oz is understandably disturbed, even when he was still B-Rabbit.
- The fact that Jack completely stripped Oz of free will and forced him to slaughter an entire city. Oz couldn't do a thing about it, as he was completely under Jack's control. Also, it must have been fun to watch Alice, his most beloved person, fatally stab herself with a pair of scissors.
- It also must have been fun for Alice to hear her best friend Oz's tortured screams while he was forced to slaughter her Uncle Oswald right outside her window. And we know she heard this, because we see an image of her desperately trying to cover her ears during Oswald's murder in Retrace 99, and it's the very first thing she questions Jack about when he storms into her tower immediately after her uncle's murder (as seen in Retrace 74). When Alice demands to know how and why Jack's ignoring Oz's screams, tears, and pleas to stop (complete with an absolutely horrifying image of the now super-deformed B-Rabbit in absolute agony), Jack simply replies: "Who cares about that?"
- The part where Alice had a vision of a bunch of hands dragging her down into the Abyss was pretty horrifying in its own right. And why did no one mention poor Cheshire? Having your eyes cut out by a psycho boy with scissors is not a great way to die.
- This is more of a subtle one, but Reim tells Break that his chain has the ability to fake death, knocking the contractor out for a random period of time to complete the illusion. Also, Rufus Barma told him to keep this ability a secret from everyone in order for it to be truly effective. Now think about it. What could have happened if he'd been knocked out for a far longer period of time than he was...
- The Core of the Abyss reaching out to Alice, intending to take the Intention's other half to make her less lonely.
- What is it that Gil is cradling after he's regained all his memories? Oswald's head.