The first book is mainly safe-for-reading by innocent souls, but there is a horrifying vision at the end, with Voldemort physically inhabiting Quirrell as a parasite - his face protrudes from the back of Quirrell's skull..
Harry's in the library late at night and opens a book. It SCREAMS AT HIM!!!
"Screams at him" really doesn't do this justice. It's more like a disembodied head is trying to escape from the book, wide-mouth yelling the entire time. And, if unintentionally, it serves to foreshadow another situation where Harry encounters another face that's somewhere that isn't supposed to have a face.
Quirrell feeding off the dead unicorn in the forest. When he notices Harry and Draco, he growls.
Quirrell slithering towards Harry and Draco, looking like a cross between a Dementor and Darth Sidious.
The three-headed Cerberus acting as the first line of defense for the Philosopher's/Sorceror's Stone is pretty terrifying, even though it's a good-aligned character.
Quirrell burning alive and turning to ash from Harry's touch. His reaction at his hand falling apart was bad enough, but then there is his scream of agony when Harry uses his newfound power on the guy's face.
Hagrid, an 8.5 feet (2.6 m) tall half-giant who considers vicious and violent three-headed dogs that look like they were cast out of Hades "cute", is absolutely ''horrified'' at the mention of Azkaban. It's not made clear by this book what's so frightening about Azkaban.
Slytherin's gigantic stone face was moving... something was stirring inside the statue's mouth. Something was slithering up from its depths... Harry could almost see the giant serpent uncoiling itself from Slytherin's mouth... He heard Riddle's hissing voice: "Kill him."...
An eleven-year old girl's possessed and writing in blood on the walls. The walls which mysteriously hiss at the protagonist. Hisses and moans about it being time to kill and eat. What's not freaky about that?
"Her skeleton will lie in the Chamber forever." Pleasant dreams.
Even before the revelations of its true function in later books, Tom Riddle's diary is still deeply disturbing. Something about the fact that all the things the diary did were never really dissected and logically analyzed in-series made it all the more sickly dark, the same way that the simplistic, matter-of-fact way that dark things in children's stories and fairy tales are introduced are much more disturbing than deeply analyzed dark aspects of and occurrences in adult literature. The vagueness and mystery of the off-screen horrors combined with things that are perfectly logical, but not all neatly tied up with an explanation — like the way the diary writes back, the ink gushing out of it, the effects it had on Harry, and the things Ginny wrote in it, and, most of all, the diary's total nondescript innocence and lack of physical threats, all have a creeping Grimm's Fairy Tales type of muted horror about it.
To make matters worse, the whole Ginny story in Book Two is quite reminiscent of real-life stories of girls meeting mysterious boys online and what they often turn out to be.
The basilisk is a giant snake. In a school. Filled with children. When you look at the basilisk, you're either petrified or dead.
Acromantulas. As if the fact that they're giant, man-eating spiders isn't enough, they're also intelligent. And they hunt in packs. And one of them nearly kills Ron.
Terrible and lethal though the basilisk is, there's something about it having both eyes pecked out that's disquieting.
Ron's warning to Harry when he first picks up Riddle's diary that picking up and opening a strange book in the Potterverse can curse you for life.
Ron: Anyone who read Sonnets of a Sorceror had to speak in limericks for the rest of their life!
Lockhart was totally willing to erase Ron and Harry's memories, leave Ginny in the Chamber without even attempting to rescue her, and pass himself off as a hero, despite the basilisk still being alive and able to kill students. This man is a teacher. The students are meant to trust him and rely on him for protection.
Boggarts. Creatures that can exist without any true form is pretty unnerving, but the fact that they can take the shape of the thing a person fears most, which can change on the person's mindset, and inhabit any given corner of the globe is pretty damn terrifying. The Giant Spider form of the Boggart in the movie is a good example. See for◊ yourself◊.
"Dementors... are among the foulest things that walk this earth. They glory in decay and despair. They drain peace, hope, and happiness from the air around them." Rowling tried to dream up a demon that could scare anyone. Her solution was a monster that literally eats joy. And souls. According to her, she actually based the monsters on the feeling of depression. So basically, these things are depression made into (semi)physical creatures.
Lupin: You can exist without your soul, you know, as long as your brain and heart are still working. But you'll have no sense of self anymore, no memory, no...anything. There's no chance at all of recovery. You'll just — exist. As an empty shell. And your soul is gone forever...lost.
The GBA game of the same game has a rendition of the theme that has been catapulted onto many "most disturbing video game music" lists. Hearing it may help you to understand why.
Let's take it a bit further, shall we? Deathly Hallows implies that there's some kind of Afterlife in the Potterverse, which you can only enter if your soul is whole and undamaged. But Lupin states that when Dementors Kiss you they suck away your soul and presumably eat it or destroy it somehow, and then your soul is "gone forever... lost". Which begs the question: how can you enter the Afterlife if your soul's gone? You probably can't, and once you finally die you'll simply stop existing altogether. Not only that: the Ministry of Magic can sentence someone to the Dementor's Kiss; which means that not only they basically kill you in this life, they also take away your right to enter the eternal Afterlife. Talk about harsh punishments.
The books' description of the Dementors is horrifying enough but the third movie took it to a darker places when the viewers are treated to a close-up of one of their faces as it attacks Harry during a Quidditch game.
Wormtail betrayed Harry's parents to Voldemort, even though they were his best friends. When his remaining friend, Sirius, chased him down after James and Lily's deaths, Wormtail cast a spell to cause an explosion that killed dozens of innocent people. Pinning his mass murder on Sirius and ensuring Sirius's twelve-year psychological torture in prison, Wormtail escaped. Worse, he escaped by turning into a rat and got himself adopted as the Weasleys' pet. For twelve years, the Weasley family was unwittingly sharing their home with a murderer.
And a traitor.
And the man who would bring about the resurrection of Voldemort.
Remus' transformation, in both the book and the movie. It's both the way it's clear that becoming a werewolf is painful, and that he's trying to not become a monster, as his sanity goes and his pained whimpers slowly change to growls as the wolf takes over and... yeah.
While you find out at the end of the movie that he's a good guy, seeing the Grim before you know it is pretty scary. Especially when he turns up in the beginning, when Harry's alone and he looks ready to attack.
Before The Reveal, the idea of Sirius Black himself was pretty terrifying. Voldemort's most faithful servant unhinged by his death, escaping from prison solely for revenge on Harry? All the fear of a mass murderer who's out to get you, with added magical powers that the wizards themselves couldn't figure out. Not only was he seemingly unaffected by the dementors, not only did he escape from Azkaban, but he broke into Hogwarts in a way Voldemort had not (at the time) managed to. Twice.
The trance Trelawney goes into, when she speaks her second real prophecy, is rather creepily described.
When Ron was taken away by the Grim. Sure, Sirius Black was a good guy, so they weren't in any real danger, but try thinking about it from the kids point of view: they're out after hours without permission; so no one (except Hagrid, but he's not exactly in good shape at the moment) knows where they are, and they get attacked by what is essentially the wizarding world's form of the Grim Reaper. The Grim jumps on Harry and knocks him down. He tries to bite Harry, but bites Ron's arm instead; cause he pushed Harry out of the way. Then the Grim runs off with Ron despite their best attempts to stop it and disappears into the Whomping Willow, which leads to the Shrieking Shack.
From Harry's point of view, he seems to be the dog's target. Then Ron pushes him out of the way and it bit his arm instead. Even though he's hitting with all he's got, the Dog's dragging his best friend away into unknown territory, preparing to do who-knows-what with him (main thoughts were probably visualising how badly Ron was mauled, or the dog killing Ron). And he can't run to get the teachers cause it might have killed Ron by the time they found him. Kid was probably terrified for his friend, feeling guilty for being unable to stop it, as well as out of control of the situation (helplessness).
From Ron's point of view, it's worse. Basically, no matter how hard he struggles or hits the dog, it's dragging him towards unknown territory. He hooks his foot in a tree root stop it and gets his leg broken for his troubles. Then he finds out that the Grim (which he believes is the Grim Reaper), turns out to actually be Sirius Black's animagus form, and he has Ron's wand. Keep in mind that Ron currently believes him to be an axe crazy serial killer who's probably ready to kill him at any moment, since he needs a wand in order to perform magic. This means he no longer has any defence since his wand was taken, and that he probably knows that he was bait to lure his best friend to his death. Basically, Ron's in an unknown location alone with a serial killer who could kill him at any moment with zero defence and enough pain from his broken leg and bitten arm to potentially pass out, and the only reason he's still alive is to act as bait. Sure, he turned out to be a good guy, but they obviously don't know yet. The poor guy was probably terrified out of what little mind he had left which wasn't trying to cope with a broken leg. Pretty terrifying, huh?
It's treated as a throwaway gag, but in order for the Quidditch World Cup to be held, it was necessary to inflict amnesia and varying amounts of mind control on dozens of people who weren't doing anything nastier than visiting/living in an out-of-the-way bit of the moors.
Anything to do with Muggles and the World Cup.
The second task of the Triwizard Tournament in the Black Lake in the film adaptation... the merpeople's design and their shockingly aggressive attitude when the Berserk Button is pressed.. Viktor Krum's transfigured shark head, the Grindylows, which, despite the fact that they were only seen from a distance or below, were extremely territorial...
"It looked as though Wormtail had flipped over a rock and revealed something ugly, slimy, and blind. Only worse, a hundred times worse. [...] A crouched human child, only Harry had never seen anything that looked less like a child. It was hairless and scaly looking, a dark, raw, reddish black. Its arms and legs were thin and feeble and its face — no child alive had ever had a face like that — flat and snakelike, with gleaming red eyes."
In the aforementioned scene, when Pettigrew chops off his hand, you can see the hand coming off.
Out of all the Nightmare Fuelish scenes in the Harry Potter series, one of the most unnerving has/had to be in "The Madness of Mr. Crouch". You have a possessed man, dragging himself through the forest — foaming at the mouth — talking to a tree one moment, then desperately clutching at Harry's robes the next, issuing a warning and saying his son's death was all his fault. All the while, Harry can do virtually nothing to help the situation, Viktor is useless, and Crouch Sr. still gets killed.
And then his corpse is transformed into a bone, and buried so it can never be found. And all this was done by his own son.
"I'M YOUR SON! I'M YOUR SON!" Crouch Jr. screaming and begging his father incite pure feelings of terror in that moment.
Fake!Moody reverting into Crouch Jr. and clawing at his own eye... because another eye is trying to grow in the place of the magical eye Moody had to replace his lost one.
Also, this eye itself is a little scary because it's electric blue, it can move independently from the other eye, and it can see inside Moody's head and through solid objects
And after he pulls it out, it keeps swiveling around of its own accord!
Moody was locked, bound and gagged, in his own trunk for ten months. Anyone who fears And I Must Scream will shudder at that thought.
The Unforgivable Curses. They are so-called and net a lifetime sentence in Azkaban for very good reasons:
The Imperius Curse. Imagine being forced to do things like mutilate yourself and kill others with it.
The Cruciatus Curse, painful enough that two of its victims were rendered insane for life!
That's because, in the movies, she's voiced by a human. This isn't true in the books, where all snake language is regular snake hissing, rather what's shown in the films.
The whole scene in the book where the Death Eaters first reveal themselves at the Quidditch World Cup. Even though they don't cause any lasting harm, it's made abundantly clear that they're essentially a lynch mob with magical powers. It just gets worse when the main trio runs into Malfoy, who smugly informs Hermione that they're targeting Muggles (Hermione is a witch but is in danger because she has Muggle parents). From that point on, it was impossible to ignore the real-world subtext of this series.
Malfoy: Granger, they're after Muggles. D'you want to be showing off your knickers in midair? Because if you do, hang around...they're moving this way, and it would give us all a laugh. Harry: Hermione's a witch! Malfoy: Have it your own way, Potter. If you think they can't spot a Mudblood, stay where you are.
And let's be honest: Malfoy's "knickers" line is about fifty times more unsettling if you're over the age of thirteen. To someone who's old enough to know about the concept of sexual harassment, Malfoy comes off like he's not-so-subtly suggesting that Hermione might be raped.
The scene where "Moody" tortures the spider is one of the most disturbing scenes in the series when put into context. Crouch Jr. was the man who tortured Neville's parents into insanity, and now he is performing the same thing on a spider in front of Neville just to torment him, under the guise of being a concerned teacher preparing the class for life.
Montague's experience after Fred and George stuffed him into a vanishing cabinet. He spent weeks in a pitch black limbo, hearing snatches of conversation from either end, taunting him. Eventually, he managed to apparate himself out, an experience which almost caused his death.
Made worse by the fact that it turns out that the aforementioned Vanishing Cabinet is the same one used the following year by Malfoy to create a passageway into the castle for some of Voldemort's top Death Eaters.
Not to mention how casual everyone is about it. Sure, Montague must be a grade-A douche to join the Inquisitorial Squad, but trapping him in limbo for weeks just for trying to dock you some house points? That's kind of messed up.
Harry being forced to carve his own hand open with Umbridge's quill.
The scene where Umbridge attempts to use the Cruciatus Curse on Harry. This is the wizarding version of Cold-Blooded Torture at its worst, only previously described as having been used by Death Eaters and Barty Crouch Sr.'s team of interrogators, and she's about to use it on a fifteen-year-old boy. The Cruciatus Curse is capable of causing insanity, and is considered so horrible, its use is punishable by a life sentence in Azkaban.
In the way the scene is described, she's excited, almost aroused at the prospect of using it, and keeps pointing her wand at different parts of Harry "trying to decide where it would hurt the most."
Stephen King, famed writer of such horror stories as The Shining, and creator of such memorable and terrifying villains as Annie Wilkes, called Dolores Umbridge "the greatest make-believe villain to come along since Hannibal Lecter."
The Department of Mysteries has a few moments:
The vat full of brains, and the time research room. Made even worse by the fact that the heroes saw it in the middle of the night, when it was unoccupied.
The room with the dais. An enormous, rectangular room with a sunken pit twenty feet below in the center, with stone steps leading down to it and an old, crumbling archway in the middle. The fact that the veil of this dais is fluttering with no one being there to move it is frightening enough; when you learn that it is actually the gateway to death and that the veil's fluttering is caused by souls of the dead who are waiting on the other side.
Especially creepy considering it's an amphitheatre-like room.
The love room in the Department of Mysteries. Out of all the many horrors in that place, the contents of this room is the one that they feel they need to keep behind a permanently locked door.
Hell, the Department of Mysteries itself. A top-secret government agency that only those with the highest security clearance are allowed in, inside which all of the creepiest and most dangerous magic is studied. Where have we seen this before?
Boggarts, generally all bark and no bite except for Parvati's mutant jack-in-the-box (a significantly less terrifying mummy in the book), are given a Wham Moment when Mrs. Weasley, trying to get rid of one, is forced to see the dead bodies of her family (and Harry, in a darkly heartwarming moment).Adult Fears can't be helped with the Ridikkulus spell.
The possession scene at the end of the film. Daniel Radcliffe completely sells the idea that poor Harry is being ruthlessly mind raped by Voldemort. Not to mention Harry's snake-like writhing just screams out that something thoroughly inhuman is trying to possess his mind and body.
The photograph of the Original Order of the Phoenix. As Harry lampshades, so many in that photo are doomed and are unaware of their fates.
Inferi (which are more or less zombies), especially when they come out of the water; Harry slashes at them, but they have no blood to shed, and they try to drag Harry down into his grave. Especially considering the fact that Voldemort's inferi are the bodies of his victims... hundreds of innocent people with families, floating in a mass grave, forced to do their murderer's bidding... The movie only made them creepier, just by making them succeed in pulling Harry under the water.
Made ever-so-much-worse in true Rowling fashion with the knowledge that one of those corpses is Regulus Black, Sirius's kid brother.
The potion in the cave. It's freaking Dumbledore sobbing and pleading for Harry to kill him. And Harry can't do a single thing but force more and more of the potion down his throat. It's a Tear Jerker where your tears are mixed with fear.
Young Tom Riddle. He made a rabbit HANG ITSELF, among other things.
The whole thing with how similar Harry and Tom's early childhoods were fraught with abuse, and that how Tom turned out was supposed to be his own fault. Rowling even says he chose to become a psychopath, although orphanages in the twenties weren't all that great for child development, and whether one is the product of rape is directly irrelevant to whether or not one grows up to be a psychopath.
Katie Bell touching the cursed necklace, floating up with her arms outstretched, then DROPPING TO THE GROUND SCREAMING! The worst part in the movie is when we get a closeup of her face while she's being held rigid in the air. Her eyes are bulging and the angle makes her mouth look like it's open much wider than humanly possible.
That's not the only part terrifying about that scene. Even before then, when it looks like her body's getting thrown and dragged across the ground like some sort of human rag doll, it's so inhuman that it could probably give The Exorcist a run for its money.
The deleted scene where the school choir is singing that song is both beautiful AND haunting.
The fact that Muggles can feel Dementors' presence, but can't actually see them. These creatures are wandering the streets at night, preying upon victims that can't even see what their captor is.
Rowling has stated that she based Dementors on clinical depression. Taken with the above, this implies that in Potterworld, Muggles who suffer from the disorder do so because they have an invisible soul-sucking demon on them. Charming.
Apparation, when you think about it. In the books, it's merely the extremely-uncomfortable sensation of being squeezed through a narrow tube, unable to breathe, which is terrifying to those with a fear of enclosed spaces... in the films: A person's own body twisting, stretching, swirling... it's all very disturbing, especially for any unlucky freeze-frames.
Nagini in general is Nightmare Fuel, especially if you're ophidiophobic.
In the movie, before we even know that Bathilda's being possessed (unless you've read the book, of course), we have Harry upstairs alone with the poor senile old woman, while Hermione looks around downstairs. While the atmosphere is a little unsettling, you don't realize "Shit shit shit GET OUT OF THERE" until Hermione stumbles on a dark room which, when lit, has the walls and ceiling covered in blood spatter.
Snape's brutal murder. Oh, how beautiful it must be tosee his neck chewed on by Nagini, and then see him writhing on the floor in pain as blood and memories leak out from him... The movie has this as a Nothing Is Scarier moment — we see it only partially through a dirty window, and only hear the sound of the snake striking at Snape again and again.
Little scarred and blistered, soulless mewling creature Voldemort, so repugnant-looking that Harry didn't want to touch it. In the movie, it's covered in blood.
The Ministry rounding up Muggle-borns, even the children. And it's implied that a lot of them (yes, even kids) are given to the Dementors....
Fenrir Greyback's remarks about Hermione, and all of the torture scenes, despite not being graphic, are very creepy too. It's even worse in the movie. We get to see Bellatrix pinning Hermione to the ground, interrogating her while Hermione screams. Doesn't sound much more creepy than the book, right? Except then Bellatrix carves the word "Mudblood" into Hermione's arm.
The magical eye mounted on Umbridge's door, which used to belong to Mad-Eye Moody.
Umbridge during the interrogation of the Muggle-borns. Just remember that her Patronus-fueling happy thought is sending people to their deaths. She wore a horcrux in her neck, a part of Voldemort's soul and she had no trouble making a Patronus, in the presence of Dementors. Even scarier is that Umbridge was never a follower of Voldemort. She's always been loyal to the Minister of Magic, whomever that may be — unfortunately, the current Minister of Magic is under the effect of an Imperius Curse from Voldemort. Umbridge takes advantage of the situation. She already was an incorrigible sadist before Voldemort took over, after all...
The "Dumbledore corpse" that appears to anyone who enters the Black family home.
Then there's Dumbledore's sister: a six-year-old is playing happily in her garden, exploring her magic powers. Then a group of older boys appear. They do... something... to her, which causes her to suppress her magical powers and drives her insane.
Voldemort kills the wandmaker Gregorovitch, described as having a similar appearance to Father Christmas. Voldemort murdered Father Christmas.
Voldemort arrives at a Muggle house looking for Gregorovitch. The way it's described with the happy mother opening the door, her laughing children in the background, then seeing him and begging for her life and trying to protect her children... he kills an entire family just because he went to the wrong house.
Voldemort pursuing the heroes in mid air without a broom, flying like a bat out of hell.
The scene where the trio are visiting Luna's house and go into her room... and realize that she hasn't been there for quite some time. It's worse when Harry begins to calmly punch holes through her dad's excuses. Something is terribly wrong here. Later, it's revealed that Luna's a-okay.
The prologue, when Voldemort murders the Muggle Studies teacher. The whole reason he targeted her to begin with: For daring to suggest that Muggles should be tolerated and peacefully coexisted with. Knowing all the poor woman wanted was peace makes watching her die, while tearfully begging for Snape's help all the more heartrending for the viewer/reader and Snape. But it's what he says afterwards that is the true Nightmare Fuel:
Consider that a human-sized meal would take a long time for a snake to ingest. Also bear in mind that if Voldemort had other matters to discuss it would have been well within character for him to just keep talking.
It doesn't have to be anything subtly horrifying at all - just the statue's presence is dreadful. Especially for Muggleborns like Hermione, who can only stare and is unable to do much (at that moment) in protest of it.
The scene with the locket Horcrux trying to turn Ron against Harry in a last ditch effort to defend itself. Harry says "Open" in Parseltongue in order to get the locket open, and Ron is ready to stab it with the Sword of Gryffindor, but ghastly spectres of Harry and Hermione emerge from the locket, only to tell Ron that he's worthless compared to Harry, and that Hermione will never choose him. Then the spectres of Harry and Hermione start kissing, showing Ron his worst fear.
In the film, in addition to all that, when the locket opens a swirling cloud of darknessexplodesout of the locket with enough force to knock the boys off their feet. Swirling, talking, constantly having things thrusting out of it then disappearing before you can seem them properly, all while a high-pitched whirling is playing; the thing was freaky as hell. Also scary Emma Watson's and Daniel Radcliffe's perfect delivery of the lines mocking Ron, and Rupert Grint pained and horrified face as he looks the two of them making out half naked.
What happens to Lavender: She's mauled by Greyback and he starts to feed upon her from her throat. In the books, her fate is unknown, but she dies in the film. Word of God stated that she later dies of her wounds in the book canon too
Voldemort's death is... very graphic. He starts dissolving into paper like shreds, with a truly horrifying, despair-filled look on his face.
Not long before this, when Harry pulls a Taking You with Me on Voldemort, the violent and frightening way the two of them fly/fall through Hogwarts while Apparating is only made more disturbing when the two of them briefly fuseintooneimage.
And the fact they were groaning, grunting andscreaming throughout that whole fight. You could only start breathing again after they separated.
In the film, Voldemort's ultimatum to the school is accompanied by a chorus of inhuman shrieks, which is revealed to actually be coming from students. Apparently, whatever spell he was using had a side effect of mind raping random people.
The scene where Harry uses the Cruciatus Curse on Amycus Carrow can be very disturbing.
The Grey Lady pulling a Jump Scare when she suddenly screams at Harry during his search for one of the Horcruxes.
Perhaps serving also as a dark Call Back or a parallel to a more funny scene, where the other resident Ravenclaw ghost does the exact same thing to Ron six movies back, while interestingly, Harry and Ron are asking Myrtle about a Horcrux (though not knowing what a Horcrux is at the time, of course). Also more alarming considering her more serene portrayal in earlier films (and book, but let's not get into that...).
The dragon in the Gringotts underground was taught by the goblins to associate the sound of clanking metal with the pain of being stabbed with a red-hot sword. It flinches when it hears the sound. Poor thing...
The dragon itself is a pretty shockingly realistic depiction of animal abuse.
Finding out you're a living Horcrux, and have had a part of one of the most foul evildoers of the age attached to you. *shudders* Talk about getting a massive case of the heebeejeebees.
"The Warlock's Hairy Heart". A wizard decides he's above the weakness of love, and performs some sort of magic to prevent him from ever loving anyone. He tries to woo a woman to be his trophy wife, but she refuses to marry him unless he shows her that he has a heart. During a feast at his castle, he takes her down to the dungeon to show here where he keeps his ACTUAL, STILL BEATING HEART encased in a crystal casket - a heart which, thanks to lack of love is now twisted and hairy beyond recognition. The witch understandably freaks out and begs him to put the heart back in, so he cuts open his chest and puts it back in. The witch then embraces him. Time for a Happy Ending with the wizard saved by The Power of Love, right? Wrong. The warlock's heart is so completely unused to feeling love that it has deteriorated to an animalistic state, driving the wizard to find a true heart. He does this by cutting out the witch's heart and trying to magic out his own. The dinner guest then find him downstairs both hearts in his hands with him licking the witch's heart.In the liner notes, Dumbledore even points out that many wizard parents won't tell it to their children "until they're in an age where they won't have nightmares".
The Lethifold: A living shadow that attacks the sleeping, enveloping and devouring them whole, leaving no trace behind. The only way to repel them is with the Patronus Charm, which not every wizard/witch can do.
And for some nice Fridge Horror: Consider how many Muggles living in its habitat (which thankfully is limited to the tropics) may have been devoured by it without any witnesses or clues. Their family and friends would never know what happened to them. Were they kidnapped? Did they run away? Why? Are they still alive? A loved one could easily be haunted by such a mystery for the rest of their lives. Even if they were wizards and knew of Lethifolds, they could never really know if the victim was eaten by one or if something more conventionally sinister happened...and again, by extension, whether they were still alive.
The footnote even points out that it's nigh impossible to count just how many people were eaten by Lethifolds, with an easier number being people who fake Lethifold attacks for one reason or another.
The Nundu: A gigantic leopard that moves silently, has breath virulent enough to wipe out whole villages, and has never been taken down by less then a hundred wizards working together, which makes it about as powerful as 40 dragons* 4 dragons can be handled by abut 10 wizards.. Small wonder that it is considered the most dangerous creature in the world.
Harry Potter And The Deathly Hallows, Harry Potter And The Prisoner Of Azkaban, Harry Potter And The Philosophers Stone, Harry Potter And The Chamber Of Secrets, Harry Potter And The Goblet Of Fire, Harry Potter And The Order Of The Phoenix, Harry Potter And The Half Blood Prince