Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: Hunter: The Vigil
Hunter: The Vigil takes all the horrors of the New World of Darkness and adds the layer of potential insanity. You can't let your loved ones know what's happening, because they'll either think you're a loony or be put in danger. Vampires could have control over your job or the police, so you can't just go around staking every bloodsucker you see or you'll find yourself out of a job and under arrest. Werewolves are stronger, faster, and more vicious than you and won't hesitate to tear you to shreds. You can't kill ghosts with bullets, and they can possess you. Slashers have no human morals or code, and would just as soon slice you up than say hello. Even Prometheans are frightening, since they are unnatural aberrations and a sin against all nature and reason. The changelings are probably the worst, since they had no control over what happened to them and are sometimes so twisted they cannot interact with human beings without harming them in some way. The worst part of it all is the fact that a hunter must make a moral decision, slowly wearing away at themselves until the line between man and monster is nearly nonexistent.
Let's look at the list of horrors that being a Hunter means having to face, shall we? Before and after you learn more about what they actually are from their perspective?
Walking, blood-sucking corpses that claim to rule the night — and there's not only boasting in that claim. They can charm and manipulate with the skill of consummate predators; part of this is natural, but part of this is something supernatural. They can bend people's minds with a look, a word, a thought, control animals and read their thoughts, or inspire terror by their mere presence. They can become invisible, they can meld into the ground underfoot, a wall, a tree, anything. They can roam the night in the shape of a beast or as a wandering bank of mist. They can move faster than a human can blink, shrug off being hit by a car, punch through a brick wall, or worse. Their blood is the ultimate intoxicant; and drink it too often, and you become their slave, in mind, body and soul. They don't really feel pain, so unless you know their weakness, they just keep soaking up every bullet, blade, arrow, punch, anything you throw at them until they have their fangs in your throat.
The reality: Everything about that perception is true. Except not, because there's a part of the vampire that is still human, still capable of remorse for what they do. And it's going to lose the battle against the creature they are now, and its utterly amoral predatory instincts. It's only a question of when...
Werewolves — every nightmare you ever had about the wolf come to life in one gore-dripping package of killing machine. They could be anyone, and you won't even know it until they come for you. They can wield weapons with human skill, then turn into a monster and rend you limb from limb with bare fangs and claws. They heal almost as fast as you hurt them, and their mere presence makes you want to curl into a ball and weep for mercy. What's worse? They have Black Magic too! They can do...things that shouldn't be possible, and you can never tell what a werewolf is capable of until it's too late — some can hurl fireballs, others can make your weapons betray you at the worst possible time.
The reality: They're guarding the world against something even worse. Well, a third of them are; the rest are fascistic, bloodthisty nutcases who regard that previous opinion as an ideal to be achieved.
Witches, people who have sold their souls to the darkest powers for dark blessings and foul boons. They can raise the dead against you, turn you into lifeless stone, call down thunder and lightning, flame or worse against you. They can manipulate fate itself so that bad luck comes your way until you die — without ever tracing it back to the witch responsible — or bend time and space like playthings. They're unnatural, too powerful to trust, and could be anywhere.
The reality: They regard the infernal barginers with the same fear you do; they just had a crazy dream one day and suddenly realized they could do magic. Anybody could become one. You could become one, and are more likely to than many. And a few of them have gone exactly as power mad as you thought. And they rule the world.
Twisted walking dead men, like a cross between Frankenstein's Monster and The Golem. They feel nothing for humans besides envy and spite and hate, so they lash out with all their awful power at random, and wherever they go, the earth itself suffers from their presence. Some poison the water into a toxic sludge, others make the wind foul or cause the very earth to rot into dust, while others cause fire-storms, rip open holes between reality and... someplace else, or create the freezing desert of tainted dust that is a nuclear winter.
The reality: Most of them are almost harmless, men and women made of the dead, who seek only to purify themselves until they become a true, living human. However, even if you know this, you can't stop yourself from hating them; it's an inescapable part of what they are, that all who truly live despise them. What's more, where they walk, they awaken monsters, creatures that seek to feed on them but are forced back into sleep by normal humans... and will do anything to stop it. And some of them have abandoned their quest for humanity, embracing the monstrous nature at their core. They herd those monsters, hunting their own kind... and being everything you fear about the others.
Ancient undead sorcerers whose power and might are Biblical in scale. If you value your life, never, never disturb their resting places - or worse yet steal from them - otherwise not all the powers of Hell will be enough to save you. They are relentless, implacable, and indestructible, like ancient Terminators - they will find what they're after, no matter what stands in their way. And should they reveal their true selves, the sheer weight of time will crash down on you, sending you running for your life.
The reality: They do this because their gods tell them to.
Demons. Literal, bona fide, no shit, goddamned (literally) Fallen Angels who rebelled against the Creator for personal reasons, and now walk the Earth as false humans. They are utterly selfish, completely amoral, and capable of perfect lying to get what they want-up to and including a promise to steal your soul, hollow it out, and then wear it like a suit so they can take over your life. Or the life of someone you know. And if you corner them, they can shed it so they may better kill you.
The reality: The Creator in question? We sure hope it's only a God, because frankly, their reasons for rebellion? Completely legitimate. And the God-Machine isn't just amoral and willing to manipulate mortals for its own ends, it's a completely alien Eldritch Abomination that mutilates reality into orderly patterns by dint of its presence, and is willing to send similarly mechanical angels to force the issue. Demons are actually more human and given over to consciences then their "noble" brethren, and yet they're still evil by human standards-both out of desperation to remain free (or at least, rejoin the collective on their own terms) and because they literally don't have the same moral instincts as humans-their Fatal Flaw can easily be something like Generosity, since they view it as sabotaging their own work and those of their demonic friends for a quick feel-good act, and their Virtue can be literal Pride, as they assert their own self-will and that of their chosen organization against adversity and thus, their inherent "humanity", if such a term can apply to such alien beings. The only thing a demon has to really worry about when moral issues are concerned is the upkeep of the false human self he possesses, and they're always looking for a new one or parts to maintain it...
Other hunters, hunting you because you're in the way, or because you don't follow what they see as the right path of the Vigil. Even if you can justify killing vampires nightly, these guys are human, and humans count for murder. Some of them might have powers on par with what a witch might have. Others control the entire local area, police and politicians included. Maybe they have a secret you've worked hard to ignore ready to drop in the local news if you don't tow their line. Maybe they've finally snapped and decided that you need to die to prevent you from becoming a monster yourself. They might even be working with the monsters you've been trying to hunt. Others don't care about you, or anyone else. As long as they have what they want, you and everyone you're fighting to protect can die and mean nothing to them.
The reality: That is the reality. Still think you want to be a hunter?
Each tier 3 conspiracy in Hunter is nightmare fuel from an entirely human perspective, from the core six to the three supplement included conspiracies.
Task Force: VALKYRIE is every dangerous conspiracy theory about the US government, and really ANY government. Their authority cannot be limited by law. Their ends just barely justify the means. They are the men in black that are all too human, and at the same time completely inhuman. They are the mysterious agents making dissenters and whistle-blowers vanishing in the night. They aren't just tapping your phones, they're watching you during every waking moment. They can make you forget anything, make you their prisoner in your own skin. All for the US of A.
Have you met the Cheiron Group yet? Nice guys really. A bit of a corporate culture inside the group but still a focused organization dedicated to finding some of the science behind the monsters. If you ignore the illegal surgeries on their own people. And what is essentially torture on anyone from monsters to their own people. Did we mention the pills that may or may not be made out of dried vamp blood and given to US soldiers? And the secrets that might be behind their board of directors? Sometimes you are just paranoid. This isn't one of those times.
The Malleus Maleficarum, which literally is the book on Church Militant. Despite what it seems, a priest admitting what is said in a confessional is a gross abuse of the Church's authority, and if a priest is willing to do that it is rightfully terrifying. But no, that's not the worst of it. The worst is that unlike TFV, you can't argue that their corruption is a result of needing money and resources. The leader of the Malleus knows how vampires work, what their blood does to him, and he still drinks it. Both power and the blood have corrupted him, warping what was supposed to be a mission of divine protection into a long, rambling struggle. They still torture with modern and "classic" methods, and a third of them are willing to wage holy war on any religion that isn't Catholicism.
The Ascending Ones may be one of the more diplomatic Conspiracies on paper, but in reality, what's there is scary. See, what you have with the Ascending Ones are a group made up of one third Islamic fundamentalists, with all of the holy war-zeal you'd expect of that, and one third of ruthless drug cartels who blithely supply heroin and worse drugs to generate funding for the "glorious hunt". That's a pretty scary combination as it is, before you wrap them all together with their various noxious elixirs and tonics that let them achieve impossible feats — let's not forget, the Ascending Ones are the Conspiracy with an Endowment that can turn a human being into a vampire. Permanently. What other sorts of alchemical horrors could they be hiding in their closet? To say nothing of the implications that, like Cheiron, they've been willing to take supernatural beings apart as alchemical ingredients.
The Lucifuge — they're people who sincerely, honestly believe that they have the blood of Demon Lords And Arch Devils in their veins. They have Black Magic enough to make their claims credible. And they're determined to send every other monster back to Hell first before they end up there themselves.
The Hunt Club from Slashers is a group of serial killers who have put a points system in place to rank their murders. Their "Stereotypes" section has the "typical" Hunt Club member talk in incredibly snide terms about several of the other groups... but when he reaches the Lucifuge, he's terrified. These guys freak out professional serial killers.
The Knights of St. George are, to some extent, the Protestant answer to the Malleus Maleficarum... on the surface. Under that surface, they fear and revere "the Faceless Angels", a group of beings so powerful that just trying to communicate with one is believed to have caused The Tunguska Event. These beings are drawn by magic, and the Knights hunt and slay magic-users in order to keep their gods sleeping. They have a way to draw your deepest sins and worst elements to the surface and torture you with them. The worst part of all this? Other books have hinted at just what those Faceless Angels actually are. Without even knowing it, the Knights of St. George worship the Abyss, and everything they do makes it just a little stronger...
While not a traditional form of Nightmare Fuel (being the very definition of what a Hunter is at their best), the existence of the Knights of St. Adrian is one for Unchained and anyone else the God-Machine sics them on. Imagine - you're out there, calm in secure in the fact that the Machine can't reach you, when suddenly a perfect stranger comes up to you and literally punchesyour human form off. In a few short seconds, his buddies open fire with no end to the stream of bulletsin sight. You try to bust their cars while making a hasty retreat, but the next day, at least one of those cars, good as new, drives up to you and disgorges the same guys as before, only now a few of them are as just skilled as you were during your initial escape, having grown in skill unnaturally quick. Trying to fight back either results in the big guy you tried to gank being uninjured while a stoic looking friend suffers the harm you meant for the person who is now filling your inside with lead, or being stunned by a Hand Blast to be dragged off to a Fate Worse than Death in the angels' laboratories. Should you somehow manage to escape long enough to learn what they are though, that's when the real scary part hits - the Knights of Saint George don't actively hunt for their quarry, the angels tell them who their next target is. So the reason you've met them in the first place is that someone told on you.