# Call of Cthulhu *Created:* 2023-08-10, *Modified:* 2026-10-18 ![[Call of Cthulhu (cover).jpg|600]] **Call of Cthulhu** is the game that made cosmic horror a tabletop institution. You play an investigator — librarian, doctor, dilettante, the kind of person who refuses to leave well enough alone — who keeps peeking at the edges of the Cthulhu Mythos and pays for it, piece by painful piece of an eroding mind. Four decades on it's still the default answer to "what's a good horror RPG," which reads as either a sincere compliment or the hobby's longest-running nostalgia habit — and probably both. It's Chaosium's baby, it lives in 1920s New England (and every other decade it can reach), and its one genuinely cruel trick is making the act of *knowing too much* the point of the entire exercise. ## Setting **Call of Cthulhu** plants its investigators in the real, mundane world — most often the 1920s, where radios are new and the town of Arkham is always a train ride too close to Miskatonic University. Ordinary people — a professor, a private eye, a journalist, a rich dilettante with too much time — stumble into something that should not be: a cult, a mythos tome, a drowned god stirring in the deep. The Cthulhu Mythos is vast, ancient, and utterly indifferent: the Great Old Ones and Outer Gods are not evil so much as *other*, and human beings are small enough to look away from. The fiction is famously Lovecraft's own — the Necronomicon, Cthulhu dreaming beneath R'lyeh, Hastur, Nyarlathotep — but the tone the books actually champion is investigative and creeping: the horror isn't the monster pouncing, it's the slowly-dawning realization that the universe does not care and that you've learned something you can never unlearn. The players aren't heroes in the mythic sense; they're people trying to survive, save a few others, and — if they're very lucky — bury what they found. That's the genre's honest heart, and **Call of Cthulhu** holds it longer and more plainly than any game that came after. ## Mechanics **Call of Cthulhu** runs on the percentile bones of [[Basic Role Playing|Basic Role-Playing]] — d100, roll low, skills and characteristics measured as percentages. The signature is the **Sanity** mechanic, but the whole loop is built to pressure it. ### Character Creation Eight characteristics on a 3–18 scale: **STR, CON, DEX** (roll 3d6 each), **SIZ, INT, EDU** (2d6+6), **POW** (3d6), and **APP** (3d6) — each multiplied by five to become the percentile your rolls are measured against. From those derive **Hit Points** ((SIZ+CON)÷10, rounded down), **Magic Points** (POW), and the star of the show, **Sanity** (POW×5). You pick an **occupation** (drifters and dilettantes and bookish scholars alike) that shapes your skill list, spend points to buy skills — Spot Hidden, Credit Rating, Library Use, Cthulhu Mythos, and the rest — and roll up a personal **background**. **Luck** is a separate, spendable pool you'll come to treat like a life raft. ### Resolution To do something uncertain, roll percentile under the relevant skill or characteristic. **Difficulty** is expressed in thresholds rather than modifiers: **Regular** (roll under your full skill), **Hard** (under half), **Extreme** (under one-fifth). A roll of **01 is always a critical success**; **100 is always a fumble** (and rolls of 96–100 fumble whenever you'd need under 50 to succeed). Instead of piling on modifiers, 7th edition hands out **bonus and penalty dice** — roll an extra d10 and keep the best or worst, a neat way to speed up the bookkeeping. ### Pushing the roll Fail something and the Keeper may let you **push** it: justify, in fiction, why you get one more crack at it — you spend more time, put in more effort, take a bigger risk. You reroll once, but a pushed roll that *fails* is a fumble-grade consequence, not a mere miss. It's the mechanic that makes failure meaningful rather than annoying. ### Sanity The mechanic the whole genre is named for. Meet something unnatural and you roll Sanity; fail and you lose SAN points, with bigger hits for the bigger horrors. Drop below the thresholds and the Keeper visits you with a **bout of madness** — a rolled delusion, phobia, mania — or drops you into **indefinite insanity** when SAN falls to nothing. Between adventures you can recover your grip through therapy, but every excursion into the Mythos teaches you a little more of the wrong truth. Learning the Cthulhu Mythos skill is, mechanically, its own slow poison: it makes you more dangerous and more doomed in the same breath. ### Luck Spend Luck permanently to tilt a die result your way — and, because it never comes back, the Keeper can lean on it as a resource that forces real choices at the table. ### Combat Fights are quick and not for the faint-hearted. Initiative follows a Dexterity check; you resolve attacks with Brawl, firearms, or melee weapons against your opponent's skill; and a single well-placed **major wound** can knock an investigator out of the fight or worse. Combat in **Call of Cthulhu** is something you survive, not something you win — the game's reputation for lethal, sanity-draining scraps is earned. ## Editions **Call of Cthulhu** has been published by Chaosium since 1981, and the line's editions read like a history of the hobby's expectations creeping from dungeon-adjacent weirdness toward the grim, lit horror it's known for. - **1st Edition (1981)** — the original boxed set by **Sandy Petersen**, the book that practically invented the investigative-horror RPG and, quietly, its signature Sanity mechanic. - **2nd Edition (1983)** and **3rd Edition (1986)** — successive clean-ups and expansions of the 1e rules. - **4th Edition (1989)** — the first to really tighten the modern ruleset. - **5th Edition (1992)** — with the long-running **5.5** and **5.6** revisions; the edition many long-time players grew up on. - **6th Edition (2004)** — Lynn Willis's consolidation of the classic rules, the last of the pre-7e line. - **7th Edition (2014/2016)** — the current edition, a collaborative revision by **Paul Fricker and Mike Mason** that kept the percentile engine but rebuilt difficulty as thresholds plus bonus/penalty dice and codified Pushed rolls. *In the library (Keeper's Rulebook, Investigator Handbook, Keeper's Screen Pack, 2026 Starter Set).* ## Supplements The Mythos has a long, fecund supplement back-catalogue, and the 7th edition era has been generous about it. All of the following are **Call of Cthulhu** proper — they run on the game and were published by Chaosium as part of the line. - **Investigator Handbook (7e)** — the player-facing companion to the Keeper's Rulebook: character creation in full, occupations, skills, and the six characteristics for building a 20th-century investigator. *In the library.* - **7th Edition Conversion Guidelines** — how to upgrade your existing scenarios and investigators to the 7th edition rules. *In the library.* - **Keeper's Screen Pack (7e)** — the referee screen (text by Mason and Fricker) plus two introductory scenarios, *Missed Dues* (Mason) and *Blackwater Creek* (Dorward). *In the library.* - **Starter Set (2026)** — the boxed intro in three books: **Book 1, *Alone Against the Flames*** (a solo scenario by Mason, Fricker, and Gavin Inglis), **Book 2, Introductory Rules** (Mason with Fricker, Petersen, and Willis), and **Book 3, Scenarios** (Herber, Morrison, Sullivan, and Isinwyll with Mason, Kramer, and Spivey). *In the library.* - **[[Pulp Cthulhu]] (7e)** — the official pulp-tone dial, "two-fisted action and adventure against the Mythos" by **Mike Mason** with Bligh, Lowder, Tidball, White, Fricker, Baur, Sanderson, and Kramer: pulp talents, two-weapon fighting, and a license to be heroic in a game that usually isn't. *In the library.* - **Malleus Monstrorum, Vols. I & II (7e)** — the mythos bestiary by **Mike Mason, Scott David Aniolowski, and Paul Fricker**: **Vol. I** the monsters (shoggoths, deep ones, the whole menagerie with 7e stats), **Vol. II** the Great Old Ones and Outer Gods — plus a **Keeper Deck** of monster cards for quick reference. *In the library.* - **S. Petersen's Field Guide to Lovecraftian Horrors** — "a field observer's handbook of preternatural entities and beings from beyond the wall of sleep," written by **Petersen, Lynn Willis, and Mike Mason** and illustrated. *In the library.* - **[[Cthulhu Through the Ages]] (7e)** — the era-anthology by **Mason, Pedro Ziviani, John French, and Chad Bower** that collects Chaosium's historical settings — the Roman Empire (Cthulhu Invictus), the Dark Ages, and Mythic Iceland — into one book, so the Mythos can be run anywhere it's been. *In the library.* - **[[Arkham (Call of Cthulhu)|Arkham]] (7e)** — the Miskatonic University town itself, a 7e sourcebook built on the classic Arkham material by **Keith Herber and friends** with **Mike Mason** and **Bret Kramer** editing — mapped, peopled, and swarming with mythos. *In the library.* - **[[The Grand Grimoire of Cthulhu Mythos Magic]] (7e)** — the big gathered spellbook by **Mike Mason with Matthew Sanderson**. *In the library.* - **[[Cthulhu by Gaslight]]** — the Victorian re-casting: an **Investigators' Guide** (character and skill options for 1890s investigators by **Keris McDonald and Mike Mason**) and a **Keepers' Guide** (the 1890s London setting and its horrors, by **McDonald, Mason, Penelope Love, Mike Lay, Lynne Hardy, and David Wade**). *In the library.* - **Berlin: The Wicked City (7e)** — "unveiling the mythos in Weimar Berlin" by **David Larkins with Lynne Hardy and Mike Mason**: a 1920s campaign of decadence and occult schemes. *In the library.* - **The Children of Fear (7e)** — **Lynne Hardy**'s sprawling 1920s campaign across Central Asia. *In the library.* - **A Time to Harvest (7e)** — "death and discovery in the Vermont hills," a 1930s campaign across New England and beyond by **Brian M. Sammons and Glynn Owen Barrass**. *In the library.* - **The Shadow over Providence (7e)** — **Jon Hook**'s enhanced scenario set in the summer of **1928** in Providence, riffing on Lovecraft's own city (the Milton Hotel hosts a Tutankhamun-era Egypt exhibition). *In the library.* - **No Time to Scream (7e)** — a group-of-friends campaign by **B. W. Holland, Bridgett Jeffries, and C. L. Werner** with **James Coquillat** and **Mike Mason**. *In the library.* - **Secrets of Tibet** — **Jason Williams**' source material and scenarios set in Tibet. *In the library.* - **Doors to Darkness (7e)** — five scenarios for beginning keepers by **Brian M. Sammons, Kevin Ross, Christopher Smith Adair, Brian Courtemanche, Glynn Owen Barrass, and Tom Lynch**. *In the library.* - **Dead Light and Other Dark Turns (7e)** — two unsettling encounters on the road by **Alan Bligh** and **Matthew Sanderson**. *In the library.* - **Gateways to Terror (7e)** — **Leigh Carr, Jon Hook, and Todd Gardiner**'s "three evenings of nightmare." *In the library.* - **Mansions of Madness, Vol. 1: Behind Closed Doors (7e)** — mansion-set scenarios across the eras by **Stuart Boon, Shawn DeWolfe, Gavin Inglis, Christopher Lackey, and Mark Morrison**. *In the library.* - **Nameless Horrors (2nd Ed, 7e)** — six scenarios against the unknown by **Paul Fricker, Matthew Sanderson, and Scott Dorward**. *In the library.* - **Does Love Forgive? (7e)** — three one-to-one scenarios by **Lynne Hardy, Airis Kamińska, and Anna Maria Mazur**. *In the library.* - **Canis Mysterium** — **Scott Haartman**'s standalone scenario. *In the library.* - **A Cold Fire Within (7e)** — **Christopher Smith Adair**'s scenario. *In the library.* - **Ripples from Carcosa** — a Carcosa-themed adventure pack. *In the library.* - **Alone Against the Dark (7e)** — the solo scenario by **Matthew J. Costello and Mike Mason**, "defying the triumph of the ice" — one investigator, no Keeper. *In the library.* - **Alone Against the Frost (7e)** — the solo scenario by **Glenn Rahman with Gavin Inglis**, a solitaire adventure in Canada's wilds. *In the library.* - **Alone Against the Tide (7e)** — the solo scenario by **Nicholas Johnson**, a solitaire adventure by the lakeshore. *In the library.* - **Keeper Tips (Black)** — the collected running-the-game wisdom of a baker's dozen of keepers, edited by **Mike Mason**. *In the library.* - **Call of Cthulhu: The Coloring Book** — **Andrey Fetisov**'s official line art, "28 eldritch scenes of Lovecraftian horror for you to color." *In the library.* Several landmark campaigns — *Masks of Nyarlathotep*, *Horror on the Orient Express*, *Beyond the Mountains of Madness* — loom over the line as its most celebrated epics; they're the names every keeper hears first. ## Notes on the Mythos' other faces The Lovecraftian topic stretches well past **Call of Cthulhu**'s doors, and the garden keeps those as separate games on a shared theme rather than folding them into this family. **[[Trail of Cthulhu]]** is the same horror on the **[[Gumshoe|GUMSHOE]]** engine, clue-first and grimmer. **[[Cthulhu Dark]]** strips it to a handful of dice and a faster spiral. **[[Delta Green]]** drags the Mythos into modern conspiracy and government cover-up. **[[Elder Mythos]]** flips the table and puts you behind the tentacles. All of them are answering the same question this game asked first, and all of them are their own thing. ## References - [Call of Cthulhu (RPG) — Wikipedia](https://en.wikipedia.org/wiki/Call_of_Cthulhu_(role-playing_game)) - [Call of Cthulhu — Chaosium](https://www.chaosium.com/call-of-cthulhu/) - [Call of Cthulhu 7th Edition Keeper Rulebook — DriveThruRPG](https://www.drivethrurpg.com/product/150997/Call-of-Cthulhu-7th-Edition--Keeper-Rulebook) - [Call of Cthulhu Starter Set — DriveThruRPG](https://www.drivethrurpg.com/product/286114/Call-of-Cthulhu-Starter-Set) - [Masks of Nyarlathotep 7th Edition — DriveThruRPG](https://www.drivethrurpg.com/product/222924/Masks-of-Nyarlathotep--7th-Edition) - [Call of Cthulhu: Shadow of the Crystal Palace — YouTube](https://www.youtube.com/watch?v=T2eM3DvZbM0)