The good news is, supernatural terrors tend to follow rules. The bad news is, you might not know them, and if you broke them it might already be too late. Maybe you couldn't resist the dare to enter the woods, or being told to stay away from the creepy house made it all the more tempting. Perhaps your car broke down on the wrong backwater road, or you were kind hearted enough to lend the wrong traveller some assistance. It would have been nice if the Untrusting Community were more willing to warn outsiders (or at least have someone more credible than a creepy old man warn people), but hey, the last few ignored them anyway.
Sometimes this is an inherent part of how the horror works; the main characters have cursed themselves by doing the wrong thing or being in the wrong place. Other times, it might be more a case that they're in the hunting grounds of some supernatural creature, and have to follow the rules to avoid it (or should have followed them to avoid this situation). More often that not, the rules are consistent, but absurd, unfair or both, and creatures bound by them are more than happy to use Exact Words.
If you're lucky, maybe it's not too late to do something about it. Perhaps there's a way to break the curse once and for all, through Magic A Is Magic A. Maybe it just won't follow you once you follow the rules. On the other hand, it's often the setup for a Cruel Twist Ending (indeed, combining such an ending with this trope is effectively the horror equivalent to a Fair-Play Whodunnit, as it establishes it's entirely reasonable that the cast are already doomed). You Can't Fight Fate, after all.
Pops up in many Urban Legends and Creepypastas, especially ones that centre around performing specific rituals to a certain end. Even for ones that don't actually have any rules you must follow there's still a handy survival guide to help your chances of survival (the idea of rules in horror could be considered the ancestor of The Universal Genre Savvy Guide for any form of fiction).
Subtrope of Inevitably Broken Rule. This trope could be considered the origin of quite a few other tropes (for example, the idea of a Weaksauce Weakness comes from monsters in folklore that could be defeated by everyday items, if used correctly). It's the calling card of The Fair Folk when they're played for horror, and often how a creature subject to The Punishment operates. It is also closely related to the way Gothic Horror revolves around the Natural Order of Things (whether Nature, God, or some other cosmic structure) punishing those individuals who dared to break its rules. Taken to its logical conclusion, you end up with Cosmic Horror, where the rules are so beyond human comprehension even a slight understanding can drive you mad.
- Yu Yu Hakusho: Yuu Kaito from the Chapter Black Story Arc has an ability called "Taboo" which lets him implement word games that those within his territory must adhere to or their souls will be extracted from their bodies. Even he's not exempted from the rules of his word games.
- Pet Shop of Horrors involves Count D and his petshop of very rare and very exotic pets, many of which often can appear human to clients who are searching for something in life - a pet to help them get over the loss of a child, or to cope with unrequited love. Count D's contracts always include specific instructions in regards to taking care of these pets, including things that they are not to do. And when these rules are inevitably broken, Bad Things tend to happen to the clients as a result.
- The Laughing Salesman: Moguro Fukuzou, a humanoid Eldritch Abomination with incredible magical powers, can make any wish of yours come true for free, provided you can follow the terms of his agreement. His "agreements" usually consist of one single rule that you must never, ever break. When his clients almost inevitably do, he uses his powers to humiliate them, ruin their lives, or at times even cause their deaths (though he doesn't directly kill them). However, simply not making a deal with Moguro isn't an option — reject his services, and he'll ruin your life anyway.
- It Follows effectively turns this trope into a metaphor for an STD. Having sex with someone carrying the curse passes it on, causing a malicious spirit (taking the form of a random bystander, and only visible to anyone cursed) to relentlessly stroll towards you, killing you if it catches up and moving back to stalking whoever passed it on. The only solution is to keep moving, or pass it on and hope for the best.
- The Ring: Watching the cursed tape will attract the attention of Sadako (Samara in the US version), who'll show up to kill you seven days later. The only way around this is to copy the tape and trick someone else into watching it, passing the curse on to them. Even finding the corpse of Sadako and laying her body to rest won't help; she's too bitter and angry to let the curse go.
- The Grudge has a fairly harsh example; the moment anyone enters the haunted apartment, the ghosts begin stalking them relentlessly, killing them and making them new tortured spirits to claim yet more victims. Even leaving can't save you. The franchise eventually takes this to its logical conclusion making the curse become The Virus after it escapes the apartment.
- Trick 'r Treat: Samhain's mere presence tends to give rise to a lot of supernatural events wherever he goes, giving him a wide variety of ways to kill people who break from Halloween tradition. But as long as people give out candy, stay in costume, don't blow out the jack-o lanterns, and otherwise adhere to the Halloween "rules" until midnight, he'll leave them be. However, he doesn't take kindly to anyone murdering trick or treaters (more specifically, kids), and will go out of his way to kill the culprit, even if they do adhere to the rules.
- The Village: The titular Commune lives in fear of monsters in the woods and have a strict set of rules to avoid their attention. Subverted with The Reveal that the monsters are villagers in costumes, trying to keep the community isolated by fear.
"Let the bad color not be seen. It attracts them.
Never enter the woods. That is where they wait."
- The Gremlins series is a classic example of this trope/genre of horror. The adorable little Mogwai named Gizmo had a number of rules that anyone taking care of one needed to know. The first rule was never to place a Mogwai near bright light, especially sunlight as that would kill them. The second rule was never to get any water on them or have them drink it, as this was their primary means of reproduction, and when this rule was broken, it resulted in a number of Mogwai getting born from Gizmo's back who weren't nearly as nice as him. The third and final rule was never to feed a Mogwai after midnight (something the new Mogwai tricked the protagonist into doing by means of ripping the wires out of a mains-powered analog clock), because that would result in the Mogwai undergoing a transformation into one of the eponymous Gremlins. The key to defeating them turned out to be weaponizing the first rule, which worked on both Mogwai and Gremlins alike.
- In The Gravedancers, the protagonists draw the wrath of three angry ghosts by dancing on their graves during a drunken wake for their friend; having been encouraged to do so by a mysterious poem they found on their friend's grave.
- Ready or Not: The protagonist must spend the entire night on the mansion's grounds in a literal life or death game of cat and mouse. The rules say she can leave freely after that, however the family who own it must kill someone during the game as a sacrifice. It's not made exactly clear whether newcomers (Grace, in this case), must be the sacrifice, as several maids were offed during the game, but the family decides not to take any chances. At the end Mr. Le Bail, true to his word, allows Grace to leave with a respectful nod, and kills off the entire Le Domas family after they break the rules trying to kill her as the sun rises.
- In Dead Silence, the antagonist (the murderous ghost of a female ventriloquist) can't kill someone if they don't scream first. She does NOT make it easy to keep silent.
- The Cabin in the Woods:
- In order to ensure humanity's continued survival, every year the Organization must sacrifice a group of people to appease the Ancient Ones. These days, simply throwing someone into a volcano won't cut it, and a more elaborate ritual is needed: namely, having five sacrifices act like horror movie stereotypes via drugging, having them disturb one of many artifacts which summon monsters from deep in the Organization's vaults, and then having them hunted down by that monster. The "Whore" has to die first, and the "Virgin"'s death is completely optional. The "Athlete", the "Scholar", and the "Fool" can be killed in any order, as long as they're not the first to be killed and as long as the "Virgin" outlives them all. However, the sacrifices must be killed off before sunrise the next day. Marty, their designated "Fool", ends up becoming immune to the drugs the Organization was using thanks to his personal stash of marijuana that they missed, and survives with Dana (at least, until the Ancient Ones throw a tantrum in response). The Organization thinking that they'd killed Marty and prematurely announcing that he's been sacrificed is the first moment that gets the Ancient Ones grumbling.
- There are other scenarios playing out in other countries around the world that are meant to follow the tropes specific to the horror stories of those cultures. Only one of these scenarios is needed to succeed, but these all went Off the Rails too, causing the Ancient Ones to wake up and destroy the world.
- Hellraiser: Anyone who solves the Lament Configuration will summon the Cenobites and be dragged into their dimension. While most people who seek the box are aware of its true purpose, the Cenobites don't care either way, as Kirsty finds out when her curiosity gets the better of her. The only reason they'd make an exception is if the person was forced into it by someone else, as it is desire that summons them, not hands.
- There are three Simple Rules in "Shadows for Silence in the Forests of Hell". Don't kindle flame, don't shed the blood of another, don't run at night. Breaking them sends the shades that inhabit the Forests into a homicidal rage.
- There are many ways to kill a skinwalker. In Navajo culture, Skinwalkers can be defeated if you find out its real name. Other known ways to defeat or kill a Skinwalker is if you call it out on being one in public. You can also defeat them by getting them to talk in animal form.
- Fairies are typically depicted as beings that you do not want to cross. There are many fairy rules that you should follow, should you encounter one. Their main weakness is Cold Iron.
- Japanese myth, urban legends, and ghost stories tend to be particularly fond of this trope. Most of the popular urban legends and creepy pastas to come out of Japan have some set of rules you must follow or a special trick in order to survive.
- Some construction projects in Iceland check for the approval of the local elves via mystics that approach the construction planning committees on their behalf. Inexplicable malfunction of construction equipment and workplace accidents are sometimes attributed to displeased elves. Here are articles from NY Times and Gizmodo about it.
- Until Dawn basically has two rules; stay away from the mountains after dark (where you're at risk of being eaten by Wendigos), and don't eat human flesh while you're there, allowing the spirits to possess you and transform you into one. The latter was broken in the backstory by some miners who were trapped in a cave-in, and the former's done by the main characters, and also happens in the prologue ( which also ends with the character being forced to eat the flesh of her dead twin to survive, allowing a Wendigo spirit to possess her).
- The SCP Foundation is basically all about studying these sorts of entities...and using those rules to keep them contained (even if it costs the lives of a few "D-Class" personnel). Sometimes this is as simple as keeping a cursed item in a locked drawer, or keeping a monster in a Tailor-Made Prison. Other times it can be as bad as keeping entire towns cordoned off, and filled with highly trained (or disposable) agents.
- SCP-1384 is a humanoid statue with seemingly omnipotent powers — but it's also a pawn in a life-sized board game whose rules it refuses to divulge because it knows the Foundation wants to contain it while it wants to be free. It's fully sapient and quite chatty, but a single wrong move or misstep allows it to take a turn and move closer to freedom.
- The unnumbered SCP in the 4000 slot is heavily implied to be the (or at least a) Land of Faerie. The place has a byzantine network of rules, many of them concerned with names and the act of naming, and breaking any of them has dire consequences.
- Cat Ghost: A mysterious entity only appears when Elon looks in a mirror. The only way to make it go away is for Elon to run away from her reflection.
- The Holders Series: Each installment is a set of precise, albeit usually florid, instructions to pass the Holder's trial, with any minute deviation bringing death or worse. Success earns an Artifact of Doom in a Cosmic Horror Story, so there isn't really any winning option.
- How to Survive Camping: The whole series revolves around the list of rules written by the campsite owner, and how breaking them always ends horribly for those involved. Break rule #9note , and the lady in chains will kill you. Break rule #6note , and something will probably kill you in your sleep. Break rule #18note , and the owner will kill you, as a precaution. Break rule #4note , and the dancers may not even grant you the mercy of death. Break rule #21 note , and you really have only yourself to blame for your subsequent and completely mundane hospitalization.
- Be Cool, Scooby-Doo!: The episode "Doo Not Disturb" has a hotel haunted by the ghost of the hotel manager's deceased strict mother, who stalks those who violate the very peculiar rules placed on signs around the hotel. It's a "Scooby-Doo" Hoax, of course, perpetrated by the hotel manager's estranged brother who didn't want to run the place the same way their mother did. It turns out he wants a hostile takeover, literally, of the old hotel in spite of his success with another hotel he started on his own by scaring the guests to make it go under.