Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: Black Butler
Deals with the devil? Sounds like it should be creepy!
In Chapter 31 when Ciel and Sebastian are at Baron Kelvin's mansion and are having dinner. The "circus" show he has a few children put on isn't all that scary... Until we see a little girl on the tightrope fall and we're treated to a panel of her leg and a nice splat complete with blood squirts. Then we see two other children drag off her headless corpse, leaving a lovely, bloody trail behind. Or how about the child who was a lion tamer that's eaten right on stage? The fact that Baron Kelvin is laughing and applauding makes it all the more frightening. Then he acts surprised that Ciel doesn't like the "show" he had the untrained children put on special for him. It was a pretty disturbing chapter.
Also, he wasn't just using the kidnapped children to perform in the circus or turning them into ceramic doll parts. He kept more of them locked up underneath his manor, trying to recreate the torture Ciel underwent while he was a slave.
Thought the manga part was bad enough? Wait until you'll see the anime adaptation. You just have to hear Baron Kelvin's voice once to know he's not exactly sane.
In the first episode of the anime, a businessman comes to Ciel's house for dinner. At some point, he excuses himself and goes to answer a phonecall. Apparently, he was trying to cheat Ciel or something, of course, our favourite demon butler hears this and decides to make him pay by driving the man insane with hallucinitions to the point where Sebastian locked him in an oven. the calmness of his voice is chilling...
Ciel's flashbacks. A crazed cult leader stabbing a child in front of you? Horrific. How about a doctor who uses children's bones in his prosthetics stabbing a child in front of you the same way the cult leader did? Really horrific. Ciel got physically sick when he saw the doctor do this.
It's as bad in the anime, where there's no sign of Ciel having been stabbed, but it's implied by Angela that he may have been raped. The flashback in the 22nd episode is also pretty creepy, with a naked Ciel calmly walking (through some rather eerie white mist) on top of the piled up corpses of the cultists without any fear or hesitation in his eyes.
Drossel Keinz living dolls are terrifying for people with Dollphobia. But also the fact that he himself is a doll is quite the Fuel itself. But the worst thing for Dollphobic is the puppet of Drossels "Master".
For the few episodes he's in, Drossel is loaded with creepy. He decapitates someone on screen, uses jewelry to pick out his victims, and always has that Creepy Monotone along with the Ironic Nursery Rhyme. One noteable bit of terror is when he's talking with Elizabeth on picking a gift for Ciel before he comes to his decision, you get a close up of his face with Lizzy reflected in his eyes.
Black Butler II also has its fair share of horror, but the one scene that tops everything occurs in episode 10. It begins with Hannah talking to Ciel and saying that she has something to show him. Perfectly pleasant, right? Then her mouth opens unnaturally wide to reveal this black abyss where the inside of a human mouth would be. The eye she stole from Alois Trancy is rooted in the back of her throat, and since Ciel's soul has been partially fused with Alois's at this point, he's basically staring at himself from inside her. Hannah watches calmly while Ciel suffers a severe nervous breakdown. Also counts as Paranoia Fuel, since up to this point the episode made you believe that they were really going to hit it off as master and servant.
That bit where Claude is brainwashing Ciel into thinking he's Alois. Rewriting his past.
complete with nightmarish computer glitch-like transition between Angela's face and Ash's face. Oh man. And this troper thought only the When They Cry series could get that creepy...
Ciel's Laughing Mad moment at the end of the Circus arc in the manga is terrifying, especially considering how reserved he generally tries to be. After a massive PTSD attack in Kelvin's mansion and arguably crossing the Moral Event Horizon by burning down the entire mansion with uncountable innocent kidnapped children inside, discovering it was All for Nothing makes him... laugh, and laugh, and laugh, and babble about how humans are revolting and desperate and "even more demonic than a demon", and how he's the same. And as the ribbon off his hat is stolen by the wind, you remember that this is a thirteen-year-old kid....
Any time the bizarre dolls show up. Especially when they start acting more human- and begin repeating the same lines over and over.
The werewolf curse. First you cry, then you get rashes, your nose starts bleeding uncontrollably, your face swells up, until eventually you die in agony.
Chapter 94. The second half. Sebastian finally snaps. Thank God, it was just an act as we see in Chapter 95 (though, Sebastian did say he was 90% serious about it).
In Book of Circus's fourth episode, we watch the circus members' abduction of a young girl, which seems to involve some sort of drugging or hypnosis (possibly by using Mind Control Music) that causes her to hallucinate. The police try to stop them, but are killed by the circus crew. What really makes the scene stand out is how the girl sees the policemen as cute bears that "bleed" confetti. While the deaths we see for what they are are quite bloody, most of them are seen from the girl's point of view. It's quite unsettling to hear her laughing and clapping her hands in delight as the "bears" get offed and then happily entering the "Carriage to the Dreamland". It's even worse once you learn where the "Carriage" is actually going...
Now we know that the poor girl was being kept locked in the basement, in a perfect recreation of the cultist's room where Ciel was tortured. And in episode 9, Doctor used her for his lovely demonstration on how he extracted the material for his artificial body parts.
Book of Circus episode eight: too many things to count. Let's just say that the episode is way bloodier and creepier than manga. Oh, and Grell is back.
Book of Circus episode nine, The last shot of Sebastian while he's engulfing the building in flames. He looks downright psychotic.
Grell's reaction to viewing Beast's death record (and her "relation" to Sebastian) can either be absolutely hilarious or absolutely disturbing.
Doctor, after telling Sebastian and Ciel the whole story behind the children kidnapping, actually had a nerve to ask Ciel of hiring him! Or recommending him to the Queen because "she's not getting any younger" and "could use some maintenance". To prove how brilliant he is, he made a lovely little demonstration on how he "extracted" the material needed to make artificial body parts. Ciel snapped.
Siegliende got her legs and feet permanently broken and then tightly bound up as a part of "the Ritual" for the introduction of her as the new Green Witch. The whole werewolf story was entirely made up by the villagers to trick Siegliende into completing and then giving them the formula for a new chemical weapon, the "Ritual" was just to keep her from suspecting anything.