History TabletopGame / CallofCthulhu

''Call of Cthulhu'' has a number of similarities to that [[TabletopGame/DungeonsAndDragons other popular TTRPG system]], but is lighter on rules and easier to play. There are no classes and [[HalfHumanHybrid except in very exceptional cases]], every character is human. Each character has an array of ''D&D''-style attributes ([=STRength=], [=DEXterity=], [=CONstitution=], [=INTelligence=], [=POWer=], [=EDUcation=], [=APPearance=] and [=SIZe=]) as percentile scores. There are also a dizzying number of skills that each investigator might have a percentile score in. To perform an action, players simply roll a d100 and try to get under their score to succeed; depending on the difficulty of the action, modifiers and bonus or penalty die may be applied, or a hard or critical success (rolling under half or one-fifth of the appropriate skill, respectively) may be called for. Character progression is organic and gradual as skill points are accumulated gradually for successful rolls - if you want to learn lockpicking in ''D&D'', you'd need to take a level in rogue or have the lockpick proficiency, but here you simply get practicing, just like real life. Starting skills are determined by a vast number of occupations to choose from; from petty criminals to law enforcement (police and private detective), military types to academics, elected officials and blue-collar working men.

While ''TabletopGame/DungeonsAndDragons'' is a game of monster-slaying and high adventure, ''Call of Cthulhu'' is a game of investigation, exploration and gathering clues to unravel a mystery. Combat is rare and [[HopelessBossFight very often a suicidal endeavour]] for the investigators[[note]]Your average Fighter character from ''D&D'' might have upwards of 40 HP and be able to take several hits from a 1D6 axe before being knocked unconscious; whereas your average Call of Cthulhu investigator will rarely ever have more than 15 HP, but a shot from a .303 Lee Enfield deals 2D6+4 damage and an M1911 pistol deals 1D10+2 damage per shot (and pistols can possibly fire three times in a round). That means if someone shoots you at close range, unless your character is wearing a BulletproofVest and gets quite lucky then statistically speaking they are probably going to be either instantly killed or at least in for a very lengthy recovery in hospital[[/note]] - while shotguns and dynamite can be quite effective against human cultists and other "low level" horrors, you are hopelessly outmatched by nearly everything else in the game. In ''Call of Cthulhu'', the three most important skills in the game are Spot Hidden, Library Use and Hide, ''nobody'' wants to be saddled with the [[ArtifactOfDoom magic item]], and any player character who tries to be an ActionHero will [[DrivenToSuicide probably wind up using their precious gun on themselves to end the nightmare]].

The default setting is TheRoaringTwenties, true to Lovecraft's time period and coming with a lot of advantages for investigative horror - lack of available communication (Investigators can't just whip out their phone and call the cops if they encounter something shady like a cult gathering[[note]]And of course if the Keeper is smart they will absolutely ensure that the police are [[DirtyCop totally compromised by the same cult]], so by making that call, ''they will know'' that you know about them and [[OhCrap they can trace your phone to your exact location]][[/note]]), there are still parts of the world that are relatively exotic and unexplored, and justifiably any adult male in their twenties and thirties will have combat experience since UsefulNotes/WorldWarI wasn't that long ago). However there are also variations for other settings and time periods including:

* ''TabletopGame/AchtungCthulhu'' - UsefulNotes/WW2 setting from Creator/ModiphiusEntertainment.

* ''Cthulhu Now'' - Modern Day, would later be included in the core rule books.

* ''TabletopGame/TrailOfCthulhu'' - A sort of remake made by Pelgrane Press, using TabletopGame/{{GUMSHOE}}, a more narrativist and rules-lite system made for investigative games, instead of Call's traditional D100 system. Set in TheThirties rather then TheRoaringTwenties.
* ''TabletopGame/WorldWarCthulhu'' - UsefulNotes/WW2 and UsefulNotes/ColdWar setting from Creator/Cubicle7.

* AbuseMistake

** ''Magazine/TheUnspeakableOath'' magazine #18 scenario "Dog Will Hunt". If the Investigators investigate the Owl's Brotherhood Lodge, they may happen upon a ceremony which appears to be the HumanSacrifice of a nude woman using a scimitar. It's actually just a harmless ritual the members carry out - the woman isn't actually killed.

* AdjectiveAnimalAlehouse
** Campaign ''At Your Door'', adventure "Where A God Shall Tread". The Black Dragon restaurant can be found in Toronto's Chinatown district.
** ''Dark Designs'', adventure "Eyes for the Blind". The Black Lion Hotel can be found in in Truro.
** ''Masks of Nyarlathotep''
*** Chapter 2 "London". The Laughing Horse pub can be found in the village of Lesser-Edale in Derbyshire.
*** Chapter 5 "Shanghai". The Stumbling Tiger bar in Shanghai where the {{PC}}s can contact Jack Brady.
** ''Cthulhu By Gaslight'', adventure "The Yorkshire Horrors". In the town of Northallerton, the Investigators can obtain useful information by talking with a madman at the Red Rooster Inn.
** ''Cthulhu Britannica''. The village of Middle Harling has the Red Lion pub.
** Supplement ''Green and Pleasant Land'', adventure "The Shadow Over Darkbank". The adventure starts in a small hotel called the Golden Lion.
** ''Magazine/TheUnspeakableOath'' #5, adventure "The Lambton Worm". The Black Bull is the best pub in the town of Burton Green.

* AfterTheEnd: The Reaping setting described in "Cthulhu Through The Ages" is a future world where perhaps some party of investigators in the 1920s failed to prevent the rising of R'lyeh or the opening of Nyarlathotep's Great Gate. Whatever the case, the Old Ones woke up and the world screamed in pain when they did. The lucky ones died first and the surviving humans who didn't fall to the cults and the madness clung to the ashes of a broken world, hiding and waiting. The players might perhaps seek a means to cast the Old Ones back to the void they came from, or a fabled place of sanctuary and salvation away from the wickedness of the world's new masters, or maybe [[DefiantToTheEnd just take the fight to the cults in humanity's twilight]].

* ArrestedForHeroism: In ''TabletopGame/CallOfCthulhu'', investigators who attack or kill Franchise/CthulhuMythos cultists can easily get in trouble with the law. It's even common advice for Keepers to remind players that [[KillItWithFire if they try and solve every problem by burning the building down]] they ''will'' [[SurprisinglyRealisticOutcome eventually get arrested for arson, be unpaid or even sued by their employer, or otherwise face realistic consequences.]]

** ''The Fungi from Yuggoth''. On the Day of the Beast, Edward Chandler will summon the Beast (an avatar of Nyarlathotep) in Egypt. If the investigators kill him to prevent this and the Egyptian authorities capture them, the investigators will have to either prove Chandler's guilt or be arrested for murder.
** ''Adventures in Arkham Country'' adventure "With Malice Aforethought". The investigators discover an insane asylum which has had all of its staff murdered by a Myth/CthulhuMythos creature. When the investigators manage to stop the creature's rampage, they are arrested by the police and tried for the killings.
* AttackOfTheMonsterAppendage: ''Dreamlands'' adventure "Yellow Sails". When Mironim-Mer activates the Oracle Mirror, the wendigo demon possessing it sends out a tentacle to grab him.
* AwkwardSilenceEntrance: Supplement ''Adventures in Arkham County'', adventure "The Whore of Baharna". When the PlayerCharacters enter the Scarlet Witch pub in the city of Baharna, the crowd falls silent. Once the crowd members have checked the [=PCs=] out, they start talking again.
* BackAlleyDoctor: Supplement ''The Asylum and Other Tales'', adventure "The Auction". Dr. Verhamme claims to be a doctor but can't provide a diploma or any other proof. He spends most of his time performing illegal abortions. When he was called in to treat Klaus Hunderprest's wife, he diagnosed her as having incurable end-stage cancer and could do nothing for her.

* BadHabits: ''The Asylum and Other Tales'' adventure "The Mauretania". A Bolshevik agent pretends to be a priest to get close to a Russian count for an assassination attempt.

* BedouinRescueService: ''Curse of the Chthonians'', adventure "The City Without A Name". After the investigators leave Irem, if they run out of camels and water in the desert they can be rescued by a small band of Bedouins.

* BeingHumanSucks: ''Cthulhu Companion'', adventure "Paper Chase". A book lover named Douglas Kimball hates dealing with people. He meets some ghouls, goes to live with them and eventually becomes one himself.

** In addition, the Throw skill which determines your accuracy with Molotovs is versatile enough that you can also use [[ThrowingYourSwordAlwaysWorks shuriken, knives]] or even stones and other [[ImprovisedWeapon improvised]] projectiles if you run out of mollies, and Throw also has a variety of noncombat uses too - distraction, tossing vital objects to teammates, etc.

* BrokeYourArmPunchingOutCthulhu: If you destroy Cthulhu with a nuke, he'll regenerate around 15 minutes later - [[FromBadToWorse but now he's radioactive]].

** The sourcebook for [[TabletopGame/CallOfCthulhuSecretsOfSanFrancisco "Secrets of San Francisco"]], a [[TheRoaringTwenties 1920s]] setting, the scenario "The Colour of His Eyes" is about some scholar who went mad looking through an alien looking telescope which allowed his to see ''Literature/TheColourOutOfSpace''. The telescope left the alien "colour", a malevolent sentient light, within his eyeballs. Now he kills or harms people just by looking at them.

* CannibalLarder: In the supplement ''Shadows of Yog-Sothoth'', adventure "The Worm That Walks". When the {{PC}}s explore the Woodie house they discover a kitchen which is the butcher shop of a den of cannibals. It has the gruesome remnants of an earlier meal spread around - hands, feet, and even more grisly bits of human debris.

* CoincidentalBroadcast: ''Magazine/TheUnspeakableOath'' magazine #10 adventure "In Media Res". Four men find themselves inside a farmhouse with the dead body of a murdered prison guard lying on a table. Each man has complete amnesia about their past. In a nearby room, a television set is showing a local newscast about the crash of a bus owned by the "Liberty Center for the Criminally Insane" and the escape of several dangerous inmates being carried by the bus. Guess what the men are?

* ConcealingCanvas

** ''The Asylum and Other Tales'' adventure "The Asylum". In Doctor Freygan's bedroom there's a painting that's slightly askew. Behind the painting is a wall safe with $5,000 worth of antique gold coins.
** ''The Vanishing Conjurer and The Statue of the Sorcerer''. At the El Profondo estate, Worlsman's apartments include a study. One important feature of the study is a portrait of Worlsman himself. If the portrait is moved it pulls away from the wall on hinges and reveals a concealed safe.
** Supplement ''The Horrible Secret of Monhegan Island''. One of the bedrooms of the Martinson home has a landscape painting on the wall. If the painting is removed, a door to a secret compartment in the wall is revealed. In the compartment is an unnamed Franchise/CthulhuMythos TomeOfEldritchLore.
** ''Magazine/{{Adventurer}}'' magazine #5, adventure "A Wee Dram of Danger". In the Kilbride house, a portrait of James Kilbride conceals the family wall safe. Inside the safe is a magical artifact that the PlayerParty needs to defeat the villain of the adventure without killing an innocent victim.
* CoolUncle: In ''The Fungi from Yuggoth'' adventure "Mountains of the Moon", an NPC named Victor recognizes one PlayerCharacter. He was an old friend of the PC's father, and the PC remembers him as "Uncle Victor", a warm, good-hearted man (even though Mom didn't seem to like him).

** ''Cthulhu Companion'' adventure "The Rescue". A group of werewolves deliberately targets derelicts; by victimizing those without friends or money, they ensure that the police are not unduly concerned.
** ''Glozel Est Authentique!'' by T.O.M.E. The Shub-Niggurath cultists in Glozel perform {{Human Sacrifice}}s using drifters and other strangers not likely to be missed.
** ''Shadows of Yog-Sothoth'' adventure "The Hermetic Order of the Silver Twilight". Carl Stanford has an enchanted cane that drains the Power from those it touches and stores them as Magic Points in the cane. He has his minions bring derelicts to him so he can drain them until they die.
** ''The Asylum and Other Tales'' adventure "The Asylum". The worship of the Great Old One called Arwassa requires a human sacrifice each month. The cultist worshippers sometimes send out kidnappers into neighboring counties to capture derelicts and vagrants for this purpose.
** ''Masks of Nyarlathotep''
*** Chapter 3 "Egypt". After Nitocris is resurrected, she creates an international organization to infiltrate countries around the world. Its task is to create a racial, religious, or economic underclass in each country that can provide HumanSacrifice victims for Franchise/CthulhuMythos cult activities.
*** Chapter 4 "Kenya". The Franchise/CthulhuMythos cultist Tandoor Singh occasionally lures in a street child or [[DisposableSexWorker prostitute]] to sacrifice to the Small Crawler, an aspect of the deity Nyarlathotep.
*** Chapter 5 "Shanghai". The Order of the Bloated Woman chooses its victims from among those who are poor and have no friends.
** Supplement ''The Horrible Secret of Monhegan Island''. The Franchise/CthulhuMythos cultists on Monhegan Island lure outcasts and loners from the mainland and use them as {{Human Sacrifice}}s because they're less likely to be missed.
** ''Magazine/TheUnspeakableOath'' magazine #18 scenario "Dog Will Hunt". A serial killer named Eben Murrow (who is also an insane Franchise/CthulhuMythos sorcerer) normally targets strangers passing through town and ne'er-do-wells who will never be missed by the locals.
** ''Magazine/WhiteDwarf'' magazine
*** #63 adventure "Draw the Blinds on Yesterday". The Cthulhu Mythos cultists who live on Southwell Farm perform {{Human Sacrifice}}s each month using hitchhikers from roads around the farm.
*** #97 adventure "A Capital Offense". In the BackStory, a Shub-Niggurath worshiping cult sacrificed tramps to consecrate an altar to their deity.
* DownInTheDumps: ''Cthulhu Now'' adventure "The Killer Out of Space". A auto junkyard's giant electromagnets can be used to trap a Colour Out of Space.

* EvilDetectingDog: Supplement ''Cthulhu Companion'', adventure "The Rescue".
** The first time the {{PC}}s meet Jael and Deborah Pelton is when they see them being threatened by a pack of dogs. The dogs are barking at them because they can detect that the Pelton girls are actually werewolves in human form.
** Later on the adventure states that all animals react nervously or angrily whenever the Peltons come near.
* EvilMask: ''Fragments of Fear'' adventure "Valley of the Four Shrines". A metal mask with Cthulhu's face grants the wearer several powers, but each time it's put on the wearer must make a SAN roll or lose sanity.
* ExplosiveLeash: The Sons of Terror's cranial bombs in ''The Fungi from Yuggoth'' adventure "By the Bay Part II".

* TheFace: ''Terror from the Stars'' section "Field Manual of the Theron Marks Society". One {{PC}} should be a Communication Specialist - a charismatic character who is a good talker.

* FictionalColor
** The Colour Out Of Space (based on the Creator/HPLovecraft story) is an EnergyBeing made up of colors outside the known spectrum.
** ''Curse of the Chthonians'', adventure "The City Without A Name". The Scepter of Iram has a gem of a color not of our spectrum.
** ''Masks of Nyarlathotep'', Shanghai section. Sir Aubrey's rocket is made of an alien metal that gleams with sickening alien colors.
** ''H.P. Lovecraft's Arkham: Unveiling the Legend-Haunted City'', adventure "Uncle Silas's Books". If the PlayerCharacters decide to burn the title magical books, the books will explode in flames that have colors unknown on Earth.

* FlyingBooks: ''Dreamlands'' adventure "The Land of Lost Dreams". While in the title place a {{PC}} can encounter some of these.
* ForensicAccounting: Many early adventures have situations where {{PC}}s can use the Accounting skill to gain information.
** ''Shadows of Yog-Sothoth'' adventure "Devil's Canyon". While examining the papers in von Varnstein's office, if one of the {{PC}}s makes an Accounting roll he can discover an order for special camera lenses. This is a clue that tells the {{PC}}s that the camera lenses they discover later are important.
** ''The Fungi from Yuggoth''
*** Adventure "The Dreamer". While searching Herbert Whitefield's office, the {{PC}}s can find bills and receipts. If one of them makes an Accounting roll, he can determine that Whitefield is deeply in debt and late on all his payments - a clue that gives him a motive in the disappearance of his client Paul [=LeMond=].
*** Adventure "Mountains of the Moon". If the {{PC}}s break into the NWI mining office's administration building and Johnathan Harris' office, they can find the site's business records. A successful Accounting roll will discover that even though the operation is performing at peak efficiency, it's still losing a phenomenal amount of money. This is an important clue that the purpose of the site is not to make money and that there's something unusual going on.
** ''Cthulhu Now'' adventure "The Killer Out Of Space". If a PC makes an Accounting roll while examining the books (accounting records) at Buddy's Best Wrex, he realizes that they aren't correct. The books are actually false: Buddy keeps the real books at home.
** ''Dreamlands'' adventure "Pickman's Student". While going through Blakely's papers, a {{PC}} can make an Accounting Roll. If he succeeds he finds receipts for four of Blakely's paintings, with the addresses of the people who bought them. Since the {{PC}}s must find the paintings in order to succeed, this is a vitally important clue.
** ''Horror on the Orient Express''. Successful Accounting rolls are useful twice: while examining Makryat's account books, they reveal that he bought and later sold a special train set, and while studying the Gremanchi Doll Work's records, they show how the Conte ordered the purchase of the Left Leg and later used it.
** ''The Asylum and Other Tales'' adventure "The Asylum". In Dr. Freygan's bedroom, there's a wall safe behind a ConcealingCanvas. It holds an account book listing the asylum's income and expenses. If a {{PC}} makes an Accounting roll, he will realize that there's no way the asylum's income could cover its expenses. This is a clue that Dr. Freygan is making money another way: by helping bootleggers smuggle alcohol.
** ''Masks of Nyarlathotep'' chapter 4 "Kenya". If the {{PC}}s make an Accounting roll while reading Ahja Singh's ledger, they discover listings of shipments to addresses in Hong Kong, London and Egypt. These are important clues that will allow them to investigate a world wide (and world-threatening) Franchise/CthulhuMythos conspiracy.
** Supplement ''At Your Door'', adventure "Full Wilderness". When a PlayerCharacter with Accounting skill is investigating Peter Tait's financial records, a successful Accounting roll tells them that Tait took money out of four different accounts to make a down payment on a farm. The farm is a site for further investigation.
** ''Magazine/TheUnspeakableOath'' magazine #18 article "The Chapel of Contemplation". If an Investigator makes an Accounting roll while searching the file system in the office, they discover a list of the title organization's income and expenses. These include many unspecifed "donations" (money received from blackmail), payments for a safe deposit box (where a valuable Mythos book is kept) and a large butcher's bill (from purchasing animals for sacrifice).
* ForgedLetter: ''Shadows of Yog-Sothoth'', adventure "The Coven of Cannich". After the witches (Cthulhu Mythos cultists) in Scotland kill Henry Hancock, they send a fake letter supposedly written by him to his nephew Jacob to cover up his death.

* FortuneTeller: A [[UsefulNotes/{{Romani}} Gypsy]] woman in ''The Fungi from Yuggoth'' adventure "Castle Dark" and Angela Broadmoor in ''Masks of Nyarlathotep'' chapter 3 "Egypt".
* FossilRevival: ''Spawn of Azathoth''. The spell Call Children of Atlach-Nacha can be used to return spider fossils to life.
* FreakyFridaySabotage: In the supplement ''Curse of the Chthonians'' adventure "The Curse of Chaugnar Faugn". Just before Professor Staunton changes bodies with the investigator for the last time, he sedates the body he's in. After he changes, he locks his old body in a room so that it will take longer for the other investigators to find the body and figure out what's going on.
* FreshClue: ''Terror Australis'' adventure "Old Fella that Bunyip". The Investigators may stumble upon the scene of one of the Bunyip's attacks. They find a picnic site with signs of a struggle and a tea kettle of water heating over a fire. The kettle is still whistling, which means they arrived minutes after the attack.

** For the most part, it's still quite [[{{GameplayAndStoryIntegration}} integrated]] with some amounts of [[{{ZigZaggedTrope}} zig-zagging]], and it depends at what a Keeper is willing to throw at his players. As far as deity-level Mythos entities (Great Old Ones, Elder Gods, not even to mention the Outer Gods) are concerned, they ''are'' by definition immortal, being able to reform and come back some time (minutes to years) after being banished, and functionally invulnerable. The latter also goes for the higher-level Mythos entities (dholes, Cthonians, Star-spawn, the iconic shoggoths, Flying Polyps, hunting horrors, star vampires, Terrors from Beyond...), any of which will generally kill the entire party two times over before they manage to put more than a scratch on it, unless the party is exceptionally lucky ''and'' marvelously well-equipped. However, the lower-level entities that could pass for "Mythos footsoldiers" (ghouls, zombies, Deep Ones, the occasional dimensional shambler or two) can indeed be kept at bay and killed with [[MoreDakka sufficient firepower]] or the right kind of weapons, although it's still not exactly trivial. Human cultists, being mostly equal in stats to player characters, can be slaughtered in numbers if the investigators have the tactical advantage. Unless the cultists have one or several Mythos sorcerers with them, then the party is screwed once again. (And of course, another problem with human cultist enemies is that, while substantially weaker than almost any Mythos entity, they have the ability to use human technology just as well as the investigators - so the wondrous properties of shotguns detailed below can also work ''against'' the party...)
* GeneticMemory: ''The Fungi from Yuggoth'' adventure "Sands of Time". Both the archvillain and the player characters experience an awakening of ancient genetic memories stored in their DNA.
* GiantSpider: In the ''Dreamlands'', Leng Spiders can grow to huge size and weigh hundreds of tons.
* GloriousLeader: ''The Fungi from Yuggoth'' campaign. The Brotherhood of the Beast plans to cause worldwide disaster so its leader can step in, save the world and be made President of the U.S. (and eventually ruler of the world).

** ''Dreamlands'' campaign setting, adventure "Pickman's Student". While exploring the dream version of Elder Yuggoth, the {{PC}}s can encounter 4 dully glowing green gems that some Mi-go are using to restrain a Dark Young of Shub-Niggurath. Later on, the {{PC}}s see one of the Mi-go sacrifice the Dark Young with a knife that has a blade made of the glowing gemstone.
** Campaign ''Spawn of Azathoth''. The Investigators can acquire two stones that are necessary to deal with the Seed of Azathoth. At the climax of the adventure, the stones become strange fist-sized, glowing ovoid gems that increase greatly in weight.
** Supplement ''Fragments of Fear'', adventure "The Secret of Castronegro". The sorcerer Bernardo Diaz has a magical ruby ring which glows brightly whenever it heals damage he's taken. The ring will also glow the first time it is put on someone else's finger.
* GoMadFromTheRevelation: TropeNamer (the phrase is taken from the same paragraph quoted above). When the characters realise just what is going on, their Sanity often snaps. As they learn more about how the world ''really'' works (the "Cthulhu mythos" stat), their maximum Sanity permanently drops by an equal amount. Thus, someone with a perfect Mythos score, having learned everything there is to know about the universe, would have no Sanity at all. These people usually wind up gibbering in the corner of a padded cell for the rest of their lives... or they run off to join a Mythos cult.

* TheGreys: Featured in TabletopGame/DeltaGreen. [[spoiler:They're actually artificial life forms created by the Mi-go as part of their experiments on humanity.]]

* GunsAreUseless: Nothing you can lift is high caliber enough to even scratch Cthulhu. Even heavy artillery won't stop him for long. In comparison, Cthugha is a sentient ball of intense heat. Firing soon-to-be blobs of molten metal at him kinda tickles. However, they do a bang-up job on human cultists and low-level Mythos minions, though, so if you find a group planning to call forth either of the above, break out something high caliber.
-->"So what happens if you nuke Cthulhu? He reforms ten minutes later, but now he's radioactive!"
** Heavily averted in the ''Pulp Cthulhu'' variant play, where just about every [=PC=] is likely to have high skill with at least one firearm and gunfights are much more common.

* HandcuffedBriefcase: Supplement ''Horror on the Orient Express''. Franklin Myers carries the Franchise/CthulhuMythos TomeOfEldritchLore ''Unausprechlichen Kulten'' in a briefcase handcuffed to his wrist.

* HighVoltageDeath: Supplement The Asylum and Other Tales, adventure "The Asylum". Doctor Freygan's laboratory has a tub into which victims are placed in order to turn them into proto-shoggoths. If a living person is in the tub when the apparatus is activated, electrical bolts slam into their body and instantly (and horribly) kill them by electrocution.
* HollywoodTorches: ''Worlds of Cthulhu'' magazine #3, adventure "The Golden Scorpion".

* HydePlaysJekyll: ''The Asylum and Other Tales'' adventure "The Madman". Adam Smythe has a split personality. His evil side pretends to be his normal personality whenever it's in control.
* HypnoFool: Adventure ''Pursuit to Kadath''. During a party, Nils Lindstrom is hypnotized as part of a game. He is subjected to all of the normal pranks that hypnotized people are subjected to, such as being ordered to act like an animal, demonstrate alternate personality traits and undergo age regression.

* InheritanceBacklash. This is a staple of ''Call of Cthulhu'' published adventures, to the point that savvy players, if they inherit an old house, will not go there until they've stocked up on the blowtorch fuel.
** Supplement ''The Asylum and Other Tales'', adventure "Black Devil Mountain". A PC receives some property as a bequest from their recently deceased brother. It turns out to be near the site of some extremely nasty Franchise/CthulhuMythos activity.
** ''H.P. Lovecraft's Arkham: Unveiling the Legend-Haunted City'', adventure "The Books of Uncle Silas". When one of the PlayerCharacters inherits his Uncle Silas's estate, he also receives the attention of a psychotic murderer who wants to obtain Uncle Silas's collection of Franchise/CthulhuMythos books.

** ''Magazine/WhiteDwarf'' magazine #68 article "Crawling Chaos - Free the Spirit". When a person is hypnotized, they may be given simple commands. However, they can try to resist following any command that is strongly out of character (such as requiring them to kill or be reckless).

* KillItWithFire: ''Terror from the Stars'', "Field Manual of the Theron Marks Society". An "Indian Water Pump" filled with gasoline can be used as an improvised flamethrower. Spray the monster with gasoline, then set it on fire.
* KidnappedByAnAlly: ''Pursuit to Kadath''. The investigators are kidnapped by a group of armed men and taken to meet U.S. Senator Harold Lindstrom, who wants to hire them to find his son Nils.
* KindRestraints: ''Masks of Nyarlathotep'' adventure "The Derbyshire Murders". Eloise Vane becomes a werewolf on nights with a full moon, so her father and brother lock her away in the castle dungeons then.

* LostInTransmission: The Roman legion scribe's account in the ''Cthulhu By Gaslight'' adventure "The Yorkshire Horrors"

* LuredIntoATrap: ''Shadows of Yog-Sothoth'' adventure "The Worm That Walks". Mr. Edwin sends the {{PC}}s into several situations where they're guaranteed to be attacked.
* MacGuffinDeliveryService: Supplement ''Horror on the Orient Express''. The two main villains of the adventure, Mehmet Makryat and the vampire Fenalik, cannot acquire the pieces of the Sedefkar Simulacrum themselves. They trick the Investigators into gathering the pieces for them and try to steal the pieces from the Investigators.
* TheMafia: Encountering the local organized crime is very common in period modules, with mobsters often trafficking in mythos objects. One such example is Zeke "The Geek" Crater from "Mansion of Madness."
* MagicIsAMonsterMagnet: ''Cthulhu Companion'' adventure "The Mystery of Loch Feinn". While in the underground area of Castle [=MacLaireag=], any spell casting doubles the chance of a lloigor detecting and attacking the investigators.

* MoralityChip: Inverted in "The Fungi from Yuggoth'' adventure "By the Bay". A MadScientist uses electrical brain implants that can control human beings, to create terrorist criminals and convert a U.S. Treasury agent into TheMole.

** Supplement ''The Asylum and Other Tales'', adventure "Black Devil Mountain". The Investigators ({{PC}}s) can hire an Indian guide named Black Tom. He claims to know the area (and especially the mountain) quite well, but has a sinister manner. He once guided five hunters to the mountain: two were killed, one went mad and two were never seen again.
** Supplement ''Curse of the Chthonians'', adventure "Thoth's Dagger". When the Investigators arrive in Cairo they are approached by a person who offers his services as a dragoman (guide) to show them around the city.
** Supplement ''The Fungi from Yuggoth'', section "Mountains of the Moon". When the Investigators arrive in the village of Huancucho they can hire a native guide named Sancho who can guide them to the New World Incorporated mine.
* NaughtyBirdwatching: ''The Asylum and Other Tales'' adventure "The Auction". An astronomer has a telescope in his apartment which he uses for his secret hobby, voyeurism.
* NeckSnap: Supplement ''Fearful Passages'', adventure "Sleigh Ride". A giganteus does it to Professor Chance.
* NeverSmileAtACrocodile: The game had all sizes of crocodiles. In the "Valley of the Four Shrines" adventure in "Fragments of Fear" they could be encountered as wandering monsters.

** ''The Asylum and Other Tales'', adventure "Black Devil Mountain". The town of Indian River only has one general store. When the owner found that the recently arrived NonPlayerCharacter Albert Goddard was living on Black Devil Mountain, he refused to sell anything to him and Goddard had to travel seven miles away to the town of Addison for supplies.
** ''Mansions of Madness'', adventure "The Plantation". The Gist general store is the only one in the area. If the {{PC}}s want to buy supplies, they'll have to go there.
** ''The Fungi from Yuggoth'' adventure "Mountains of the Moon". The village of Huancucho in the Andes mountains of Peru has only one place to buy things: a small trading post which carries tools, canned food and other items.
** ''Shadows of Yog-Sothoth'' adventure "The Coven of Cannich". The only store in the small Scottish town of Cannich is owned by Jamie [=MacNab=].
** Supplement ''Terror Australis'', adventure "Pride of Yirrimburra". The small Australian town of Yirrimburra has only one general store, the source of manufactured goods and luxuries.
** ''Adventures in Arkham Country'', adventure "The Dark Woods". The small village of Dunwich, Massachusetts has only one shop: Osborn's General Store, which is housed in an old church.
** ''Magazine/TheUnspeakableOath'' magazine
*** Issue #8/9, adventure "Dark Harvest". The only store in the town of Oak Valley, Iowa is Harv's General Store. Unfortunately for the investigators, the owner of the store is a member of the cult that infests the town.
*** Issue #19, adventure "The Brick Kiln". The village of Trevor Major only has one shop, a general store run by Mrs. Alderson.
* OperatorIncompatibility: ''Terror from the Stars''. Mi-Go fire their LightningGun by grasping it and altering its electrical resistance. Humans have to clip one of its wires.
* OracularHead: ''The Asylum and Other Tales'', adventure "The Auction". A magical Brass Head could animate and answer questions if it were covered with burning blood.

* OurCentaursAreDifferent: The T.O.M.E. (Theatre Of the Mind Enterprises) supplement ''Pursuit to Kadath'' has the Dragon Warriors, a set of monsters created by the Cthulhu Mythos deity Yig. One of them is Choara, a giant black scorpion with the torso, arms and head of a human.

* PartialTransformation: Proto-shoggoths in ''The Asylum and Other Tales'' adventure "The Asylum" and the werewolf Eloise Vane in ''Masks of Nyarlathotep'' chapter 2 "London" adventure "The Derbyshire Monster".
* PhlebotinumOverdose: ''Terror Australis'' adventure "Old Fellow That Bunyip". The investigators must drive a bunyip upriver by calling "Eleanba Wunda", the name of a terrifying spirit which will appear if the name is said too often.
* PitTrap: ''Worlds of Cthulhu'' magazine #3, adventure "The Golden Scorpion".
* PlaceOfProtection: ''Fragments of Fear'', adventure "Valley of the Four Shrines". A path surrounding a lake prevents zombies from passing over it, protecting a human fishing village from them.
* PlanetaryParasite: The boxed set ''Spawn of Azathoth''. If a Seed of Azathoth strikes a planet, it can penetrate it and grow into a Spawn of Azathoth the size of a star. All that's left of the planet is shattered ruins. The former fifth planet of the solar system suffered this fate: its remains are the Asteroid Belt.
* PlayfulPursuit: In the supplement ''Curse of the Chthonians'' adventure "Dark Carnival", Lucy Pringle and her boyfriend Kent Howard are strolling along a riverbank. Kent tries to kiss Lucy and she runs away laughing, calling out "If you can catch me, you can kiss me!" Kent races after her, trying to catch her and earn the kiss.

* PolarMadness: In the supplement ''Fearful Passages,'' the adventure "Sleigh Ride" features this: while sledging along the Vitim river in Siberia, the Player Characters will experience the purga, a fierce Siberian blizzard. They have to spend three days in a shack and start suffering from cabin fever. During that time they hallucinate that they hear music, impassioned sighs, nursery rhymes and screams. When they go outside, they see apparitions of ancient memories, old friends, fields of dandelions and shrouded skeletons.

* PossessingADeadBody: ''Magazine/WhiteDwarf'' magazine #87 article "With a Pinch of Salt". One method of creating a zombie is to summon and bond a Franchise/CthulhuMythos monster to enter and possess a corpse. Normally only a monster that isn't tied to a physical body can be used, such as a gaseous Fire Vampire or a ghost.

** ''Cthulhu Companion'' adventure "The Secret of Castronegro". Bernardo Diaz has lived for 300 years due to the ruby ring he wears. If it's removed from his finger, he will instantly die and his body will shrivel.
** ''The Fungi from Yuggoth'' adventure "By the Bay Part I". Lang Fu's Coat of Life has allowed him to live for centuries. If it is ever removed for more than a few minutes, his body will begin an irreversible aging process that will cause his rapid death.
** ''Masks of Nyarlathotep'' campaign, chapter 3 "Egypt". Omar Shakti, the high priest of the Brotherhood of the Black Pharaoh, is several thousand years old. If the investigators kill him, his body will immediately crumble to dust.
** ''Magazine/WhiteDwarf'' magazine issue #67 article "Haunters of the Dark". One of the possible powers of ghosts is to age a victim by ten to thirty years, which can drain points of Strength, Dexterity or Constitution. Each point drained gives the ghost 1-3 points of Power.

* RealityWarper: Hounds of Tindalos, Tindalosian Hybrids, and Lords of Tindalos all have limited localized space-warping abilities.
** In the d20 version the great old one Tsathoggua has the ability to reshape reality. It uses it to swallow things larger than itself or to kill and resurrect those who don't approach him respectfully enough until they learn their lesson.
* RedEyesTakeWarning

** Supplement ''Dark Designs'', adventure "The Menace from Sumatra". The evil Vibur (AKA The Thing from Beyond) has three triple lobed burning red eyes.

* {{Retcon}}: As of the the fifth edition, the game discards the entire Good vs Evil aspect Derleth tried to jam into the Franchise/CthulhuMythos, returning to Lovecraft's original vision.

** Also, increasing your knowledge of the Cthulhu Mythos can not only cost you sanity points during the learning process, but permanently lowers your ''maximum'' Sanity. At Cthulhu Mythos 100, your Sanity is 0 by default - in other words, it is impossible to truly understand what the universe is without going stark-raving mad.
* ScoobyDooHoax: ''The Asylum and Other Tales'' adventure "Westchester House". The Investigators (PlayerCharacters) will hear stories of several unnatural events that indicate that the house is haunted, but they're all fake, mostly done by people trying to make it appear that way to cover up their own schemes.

** ''Magazine/TheUnspeakableOath'' #7, adventure "Convergence". The adventure takes place in Groverville, Tennessee. One of the stores in town in town is called the Stuffer Shack. This is a reference to the TabletopGame ''TabletopGame/{{Shadowrun}}'', which has the company Stuffer Shack as an InUniverse version of 7-11.
* SickbedSlaying: ''The Fungi from Yuggoth'' adventures "The Dreamer" and "The Worm that Walks".

* SmolderingShoes: ''Curse of the Chthonians'' adventure "Dark Carnival". A man is pulled through the iron bars of a gate by ghouls: when his feet get stuck, they're ripped off, leaving them (still inside his shoes) on the ground.
* SoulJar: ''Shadows of Yog-Sothoth'' adventure "Devil's Canyon". The spectral hunters cannot move more than 1 mile away from their kachina dolls, which hold their souls. If a specific chant is conducted over a spectral hunter's doll, it is destroyed.

* SpeakOfTheDevil: ''Terror Australis'' adventure "Old Fella That Bunyip". To drive Bunyip upstream the investigators must say "Eleanba Wunda", the name of a evil spirit which will appear if its name is chanted too often.
* SplitPersonality: ''The Asylum and Other Tales'' adventure "The Madman". An investigator is driven insane by exposure to the Cthulhu Mythos and develops an evil alternate personality.
* SpeedDemon: The ''Fearful Passages'' supplement, adventure "Furious Driving" has Rupert Putney, the main NonPlayerCharacter. He [[DrivesLikeCrazy drives like a maniac]] at incredibly high speeds (for the 1920's, anyway).

* StealthHiBye: Supplement ''At Your Door'', adventure "After the Big One". The PlayerCharacters may meet and talk to a musician named The Royal Pant (actually the Franchise/CthulhuMythos deity Nyarlathotep). When Nyarlathotep gets tired of talking to them, they will be momentarily distracted. When their attention turns back to him, he will have mysteriously disappeared.

* SufficientlyAdvancedAlien: Most Great Old Ones (and a few species) are described thus, possibly overlapping with outright godhood. Despite common belief, Cthulhu is ''not'' a god; terrifyingly he is actually the alien high priest of a god far, ''far'' more horrible than he is - Azothoth, the slumbering nuclear chaos.
* SummonBiggerFish: ''Terror From The Stars'', "Field Manual of the Theron Marks Society". When facing powerful monsters, summon another deity or monster that hates whatever's attacking you.

* SundialWaypoint: ''Terror from the Stars'' adventure "The Temple of the Moon". In the temple there is a light shaft that allows moonlight to enter, and a pool with a map on the bottom. If the Tablet of the Moon is placed atop the light shaft at midnight under the light of the full moon, the moonlight will be refracted into a bright point of light on the map, showing the location of the main temple of Shub-Niggurath.

* SuperSpit: ''Magazine/{{Polyhedron}}'' magazine #124 article "Modern Minions of Cthulhu". The Jersey Devil can spit its acidic spittle up to 5 yards. It does 2-12 HitPoints of damage to any creature it hits.
* SwordCane: One of the new Victorian Age weapons in ''Cthulhu By Gaslight'' was the sword cane.

* TakingTheBullet: "The Asylum and Other Tales" adventure "The Mauritania". Bodyguards have the skill Block, which allows them to hurl their body in between an attacker and the person they're protecting.
** In ''Pulp Cthulhu'' the skill is instead had by various BigBad characters and is called "lookout master!" To avoid the BigBad dying to a good hit too soon, a mook will lunge in and take the hit for them.

* TarotMotifs: A [[UsefulNotes/{{Romani}} Gypsy]] FortuneTeller uses Tarot cards in ''The Fungi from Yuggoth'' campaign, section "Castle Dark"

* ThankYourPrey: ''Terror Australis'' adventure "City Beneath The Sands''. Power Boy could call animals and ask that they allow themselves to be eaten. If they agreed, he praised their beauty and courage.
* ThatWasTheLastEntry
** ''Shadows of Yog-Sothoth'', adventure "The Warren". The {{PC}}s take almost an hour to remove enough rubble to enter one room. When they do, they find the skeleton of a man sitting at a table and a piece of paper which is an ApocalypticLog of what happened to him - he was trapped inside the room when a disaster occurred. It ends "I am sitting now waiting for rescue. It has been eight hours."
** ''Mansions of Madness'', adventure "The Crack'd and Crook'd Manse''. Arthur Cornthwaite was trying to stop a monster that had infested his house. He was writing a note to explain the monster's vulnerability: it ends in mid sentence when the monster used its coils to snatch him into the fireplace and eat him.
** ''Terror from the Stars'', adventure "The Temple of the Moon". Professor Dermot's day books end with an entry saying that he plans to enter the Temple at night after the strange phenomena end. The {{PC}}s can find his body later: he was captured and sacrificed by the Franchise/CthulhuMythos cultists who worship at the Temple.
** ''The Asylum and Other Tales'' adventure "Black Devil Mountain". A {{PC}} receives an unfinished letter that was found among the effects of his deceased brother. The last part of the letter talks about the horrible discovery the brother had made. His body was found a few days later, dismembered and with the brain and heart missing.
** ''Dreamlands'' adventure "The Land of Lost Dreams". The {{PC}}s find the diary of Neil Bruford in his room. It tells the story of how he planned to journey to the land of Xura to find his heart's desire. The last entry says that he would reach Xura in his dreams that night. The next morning his landlady found him in a coma.
** ''Magazine/WhiteDwarf'' magazine issue #56 adventure "The Last Log". An interstellar expedition to the planet Pozalt 7 is wiped out by a Star Vampire. The mission commander Captain Spalding kept his personal log in a notebook. The last few entries say that the group has been under attack for three hours, that he assumes that the rest of the crew is dead and that he has no weapons. The final entry is an unreadable scrawl. When the PlayerCharacters find his body, his head has been ripped off and can't be found.

* ThisIsAsFarAsIGo: ''Fragments of Fear'' adventure "Valley of the Four Shrines". When the party reaches the cave that leads to the Valley, any native porters hired from nearby areas refuse to enter.

* TimeTravelersDinosaur: The supplement ''The Asylum and Other Tales'', adventure "Gate From the Past". A group of Old Ones use a Time Gate spell to travel from the Upper Jurassic to modern-day Arkham. A Ceratosaurus (carnivorous dinosaur) can be encountered if the PlayerCharacters investigating the problem use the Time Gate to travel to the past.

* TooManyMouths: ''Dreamlands'' supplement. The Maws of Pandemonium spell caused the victim's body to sprout a red-lipped mouth that gibbered and moaned as it drained the victim's magic points.
* TheTopicOfCancer: ''The Asylum and Other Tales'' adventure "The Asylum". One of Dr. Freygan's drugs is Cellular Accelerator, which can cause cancer throughout the recipient's body.
* TorchesAndPitchforks: ''Worlds of Cthulhu'' #3, adventure "Malevolence".
* TotalPartyKill: A definite possibility in case of failure. Even when things don't go disastrously wrong, a high character attrition rate is to be expected. Some players believe that the TotalPartyKill is what happens if you're ''lucky.'' If you're ''un''lucky? AFateWorseThanDeath.
** That said, the idea that ''all'' Investigators die or go insane or suffer a FateWorseThanDeath by the end of every game is a misconception. After all, Investigators can accrue skill points at the end of each session which pass over to the next one.

* TrashcanBonfire: ''Fearful Passages'' adventure "The Iron Ghost". There's one in the 1934 Southern Pacific car.

* TurnToReligion: In the supplement ''The Asylum and Other Tales'', adventure "The Asylum". God-Bespoke Johnson was originally a normal man who trapped animals for a living and wasn't particularly religious. One night he came upon a proto-shoggoth ripping apart his partner Dave Bowen. The sight drove him insane, and he became a religious fanatic who constantly preaches to anyone who will listen to him.
* TropeCodifier: For a fair number of CosmicHorror tropes, sometimes literally just by virtue of wrapping concrete game rules around things that the literary source material only obliquely hints at.
* TwoHalvesMakeAPlot: In the supplement ''Terror from the Stars'', adventure "The Temple of the Moon". The [[PlayerCharacter Player Characters]] and two independent villains each receive 1/3 of the Tablet of the Moon, a piece of gold jewelry that allows the user to find the location of a treasure on a map. The players must either defeat one or both villains and take their pieces or team up with them.
* UndeadTaxExemption: ''The Fungi from Yuggoth'', adventure "Castle Dark". Baron Hauptmann transfers his mind into a new body every few decades and assumes the victim's identity.
* UnexpectedInheritance: ''The Asylum and Other Tales'' adventure "Black Devil Mountain". A {{PC}}'s brother dies and leaves them some property which has Franchise/CthulhuMythos activity going on nearby.

* UsingYouAllAlong: ''Curse of the Chthonians'' adventure "The Curse of Chaugnar Faugn". The investigators are manipulated into helping a mad professor awaken the title Franchise/CthulhuMythos deity from its statue form.

* WhenTheClockStrikesTwelve
** 3rd Edition Main rules, adventure "The Madman". The Mi-Go have been performing midnight ceremonies in an attempt to summon the Great Old One Ithaqua.
** ''Fragments of Fear'' adventure "The Underground Menace". If the {{PC}} Investigators flee from the Dark Young of Shub-Niggurath, a week later it will summon a Hunting Horror of Nyarlathotep that will attack the {{PC}}s at midnight.
** ''Shadows of Yog-Sothoth''
*** Adventure "The Worm That Walks''. While the {{PC}} investigator is in the hospital, the title monster will attempt to establish a psychic link to him (by putting its hand over the {{PC}}'s face) each night at midnight. When it succeeds it will immediately take its true form and attempt to rend the {{PC}} to bits with its huge claws.
*** Adventure "The Watchers of Easter Island". The Crawling One (a TheWormThatWalks) performs a human sacrifice once every three days at midnight to power the moai (statues) so they can call the Messenger of the Old Ones.
** ''The Fungi From Yuggoth''. The BigBad opponent of the {{PC}}s is Edward Chandler, head of the New World Incorporated MegaCorp. He was born at midnight on Candlemas, thus fulfilling an ancient prophecy that he would bring about the Day of the Beast and allow the forces of the Franchise/CthulhuMythos to take over the Earth.
** ''The Asylum and Other Tales'' adventure "The Madman". Every four days at midnight, Adam the Bad will go out to the concrete slabs and perform a ceremony to consecrate one of them so they can be used to cast the Call Hastur spell.
** Supplement ''Dreamlands'', booklet "Dream Journeys"
*** Adventure "Season of the Witch". Ghouls are used to dig up three graves in the Aylesbury Hill Graveyard at midnight and steal the bodies for nefarious necromantic purposes.
*** Adventure "The Land of Lost Dreams". If the Investigators fail to stop the Spirit of Xura, at midnight on February 14th it will rip open Neil Bruford's body end enter our universe. This will bring despair and madness to the entire city.
** ''Masks of Nyarlathotep'' chapter 2 "London".
*** "The Derbyshire Monster". The werewolf Eloise Vane changes to monster form at midnight on nights with a full moon.
*** "Slaughter in Soho". Yalesha, a dancer at the Blue Pyramid club, will tell any investigators she encounters to meet her at midnight down the street. She tells them that once a month a truck appears around midnight and takes some Franchise/CthulhuMythos cultists to an unknown location (in fact, they participate in an evil cult ceremony at midnight).
** ''Terror from the Stars'' adventure "The Temple of the Moon". If the Tablet of the Moon is fitted together and placed on top of the light shaft in the Chamber of Worship at midnight under a full moon, the quartz lenses in the Tablet will bend the light to form a pattern of dots on the map below. The water in the pool will then refract the light dots into a single dot on the map: the location of the Temple of Shub-Niggurath.
** Supplement ''The Horrible Secret of Monhegan Island''. Whether the Franchise/CthulhuMythos ceremony takes place or not, the Deep Ones will emerge from the ocean at the ceremony site at 12:00 midnight to accept the {{Human Sacrifice}}s.
** ''Magazine/DifferentWorlds'' magazine #38 adventure "The Eye of Sitar". Azathoth cultists are planning to perform a HumanSacrifice ritual at midnight on the fall equinox. If they succeed it will result in the [[ZombieApocalypse dead rising from the grave all over the world and consuming the flesh of the living]].
** ''Magazine/TheUnspeakableOath'' magazine
*** Issue #5 article "A Tale of Terror". In one scenario, the Franchise/CthulhuMythos deity Nyarlathotep proposes marriage to captive women. If they refuse, at midnight on each night of the full moon thereafter he proposes again. If any of them accepts his offer, she is taken to the daemonic court of Azathoth until Nyarlathotep becomes bored with her.
*** Issue #19 adventure "Suited and Booted". At midnight on August 14th, the artist Patrice [=LeFevre=] will surrender himself to the Franchise/CthulhuMythos deity Nyarlathotep. The Create Wraith spell must be cast at midnight for it to work.
*** Issue #20 adventure "She Just Couldn't Stay Away (No No)". Dorothy Stotz performs a HumanSacrifice of herself at midnight in a ritual to bring her dead cat Penny back to life.
** ''Magazine/WhiteDwarf'' magazine #63 adventure "Draw the Blinds on Yesterday". The Cthulhu Mythos cultists who live on Southwell Farm perform {{Human Sacrifice}}s each month. At midnight, they kill the victims by stabbing them to death.
* WhyAmITicking: Campaign supplement ''The Fungi from Yuggoth'', section "By the Bay: Part II''. Cthulhu Mythos cultists detect Philip Jurgens as a spy and implant a small radio-activated bomb in his head. At a later time, the cultists detonate the bomb and his head explodes, killing him.

* ZombieApocalypse: ''Different Worlds'' magazine #38 adventure "The Eye of Sitar". Azathoth cultists are planning to perform a HumanSacrifice ritual [[WhenTheClockStrikesTwelve at midnight]] on the fall equinox. If they succeed it will result in the dead rising from the grave all over the world and consuming the flesh of the living.