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Chaosium · 7th Edition · System

Call of Cthulhu

Investigative horror in the shadow of the Mythos.
A short tour before your first case.

The setting

Welcome to a world that looks like ours

Trains run. Newspapers print. Police take statements. Under that ordinary surface, older things wait — and noticing them has a price.

Tone

Horror investigation, not dungeon crawling

Knowledge costs

You win by learning. Learning frays the mind. Sanity is a resource, not flavor text.

A researcher recoiling from a forbidden tome

Investigators, not heroes

You are ordinary people with a reason to ask questions. Courage is optional. Curiosity is not.

Investigators comparing notes by lamplight

The world does not care

Cosmic indifference, not a fair fight. Survive the case. Save who you can. Leave the rest to the dark.

A vast unnatural shape beyond the fog

You do not need Lovecraft memorized. The table will teach you what matters — and what you wish you had not learned.

The hobby

What is Call of Cthulhu?

A tabletop RPG of clues, conversations, and things that should stay buried. One Keeper runs the world. Everyone else plays an investigator.

Like a mystery novel

Scenes, witnesses, documents, dead ends. The puzzle is the adventure.

Unlike a dungeon crawl

Combat is rare and lethal. Talking, researching, and sneaking do more work than a gun.

The fun

Piecing the truth together — then deciding how much of it you can live with.

When & where

Most tables start in the 1920s

New England is classic — Arkham, Innsmouth, Boston — but the Mythos is worldwide. Pulp, modern, and gaslight eras exist. Ask your Keeper which map you’re on.

Why the twenties

Telephones exist. Computers do not. A letter takes days. A secret can still hide in a filing cabinet — or under the sea.

What waits beneath

The Cthulhu Mythos

The surface
Our world

Banks, churches, universities. Most people never look past the headlines.

The fringe
Cults & tomes

Whispers, rituals, books that should not have been printed. Someone always digs.

The deep
The Mythos

Entities and truths older than humanity. Naming them is half the danger.

Your job
Investigate

Follow the thread. Stop what you can. Accept that some doors stay shut for a reason.

The Keeper will reveal only what your investigators discover. Spoilers are for other tables.

Things that should not be

A glimpse of the bestiary

You may never fight these. You may only hear of them. That is often the kinder outcome.

Deep One

Sea-blooded hybrids and the cities under the waves.

Deep One

Ghoul

Tunnelers under graveyards. Hungry, patient, sometimes talkative.

Ghoul

Mi-Go

Fungi from Yuggoth. Science that does not care about your skull.

Mi-Go

Shoggoth

Protoplasmic labor that outlived its makers. Do not corner one.

Shoggoth

More entries live in the Compendium — Nightgaunts, Byakhee, Elder Things, cultists, and worse.

Who you might play

Ordinary people with bad timing

Journalists

Nose for a story. Access to presses. A habit of asking one question too many.

A 1920s journalist with a notebook

Academics

Professors, librarians, antiquarians. You know the footnotes. The footnotes know you.

A professor in a candlelit study

Professionals

Doctors, lawyers, detectives, soldiers. Useful skills. Fragile illusions.

A private detective on a rainy street

The curious

Occultists, artists, dilettantes. You wanted wonder. You found something else.

An occultist examining strange symbols
On this site

Your investigator is the center

Create a sheet, copy a public pregen, track Sanity and skills, then carry that case file into campaigns and journals.

Characteristics

STR through EDU — roll or enter, then derived HP / MP / SAN update for you.

Skills & gear

Add occupational skills, weapons, and inventory after creation.

Conditions

Temp insanity, major wounds, and the long slide toward zero SAN.

The only roll that matters

Percentile dice

Success = d100 ≤ skill or characteristic

Skills are percentages. A 60% Library Use means you succeed on 01–60. Low is good. The sheet already shows your numbers.

The numbers on the sheet

Characteristics

Eight core scores (usually 15–90). Half and fifth values are printed for hard and extreme checks.

STR

Muscle, force, lifting. Breaking doors the polite way failed.

DEX

Speed, stealth, shooting. Getting out before they notice.

CON

Health, stamina, resisting poison and illness.

SIZ

Build and mass. Hit points lean on CON and SIZ.

INT

Idea rolls, puzzles, spotting the pattern.

POW

Will, luck, Magic Points. Sanity’s cousin.

APP

First impressions, charm, looking trustworthy.

EDU

Formal learning. Fuels starting skills and Know rolls.

Derived & luck

What the sheet calculates

Hit Points

(CON + SIZ) ÷ 10. Major wounds and dying states matter long before zero.

Magic Points & Sanity

MP ≈ POW ÷ 5. Starting SAN equals POW. Both drain when the unnatural answers.

Luck, Move, Build

Luck is spent and rolled. Move and Damage Bonus lean on STR, DEX, SIZ, and age.

Keeper tip

Everyday conversation does not need dice. Roll when failure would change the story — or when fear makes the outcome uncertain.

How hard is it?

Regular, Hard, Extreme

DifficultyTarget
RegularFull value
Hard≤ half
Extreme≤ one-fifth
Critical01
Fumble96–100*

*On high skills, fumbles are 100 only. The Keeper sets difficulty; you say what you try.

Remember this

  • Bonus die: roll an extra tens die, keep the better pair.
  • Penalty die: keep the worse. They cancel one-for-one.
  • Pushing a roll: retry with a cost if you fail again.
  • Opposed rolls: both roll; better level of success wins.
  • Everyday talk does not need dice. Doubt does.
The meter that matters

Sanity

Seeing the unnatural costs SAN. Fail a Sanity roll and you lose points — sometimes a few, sometimes a collapse. Temporary insanity is a scene. Indefinite insanity is a problem. 0 SAN is the end of that investigator.

Playing it

Losing Sanity is not “going crazy for laughs.” It is fear, fixation, denial, and the story turning sharper. Lean into what your investigator cannot unsee.

Skills that solve cases

Investigation is the combat

Find the clue

Library Use, Spot Hidden, Listen, Track. The truth is on a shelf or under a floorboard.

A dim university library at night

Talk it out

Persuade, Charm, Fast Talk, Intimidate, Psychology. Witnesses are the adventure.

An investigator interviewing a nervous witness

Survive the night

Stealth, Dodge, First Aid, Firearms. Fighting is last resort — and often a bad one.

Investigators fleeing through fog

Your occupation sets starting skills. Spend points where your concept lives. The sheet is the rules brain.

When violence happens

Combat is short and sharp

Your turn

DEX order. Move, act, maybe fight back. Guns are loud. Knives are quiet. Neither guarantees tomorrow.

Damage & death

Hit points are few. Major wounds matter. A Mythos creature may not notice your revolver.

Fleeing is wise

Running, hiding, and slamming doors are valid tactics. Bravery without a plan is a funeral.

Magic

Spells exist. They cost Sanity, Magic Points, and sometimes more. Treat every ritual like a loaded gun pointed inward.

A session is scenes

Three kinds of encounter

I

Investigation

Houses, archives, crime scenes, newspaper morgues. Look, listen, take notes.

Clues on a desk
II

Roleplaying

Interviews, lies, alliances. Stay in your investigator’s voice. Dice when trust is in doubt.

A tense parlor conversation
III

Horror

The reveal. The chase. The thing in the dark. Sanity rolls. Decide who you still are afterward.

Horror closing in

A good night uses all three. Different investigators shine in different scenes — leave room for that.

Table craft

How to be a great newbie

Do

  • Say what you do and why. The Keeper narrates the world.
  • Take notes. Clues love forgetful tables.
  • Share the spotlight. Ask quieter players what they notice.
  • Play your Sanity losses honestly.
  • Ask “What do I see?” — it is always legal.

Don’t sweat

  • You do not need the whole book. The sheet and Keeper have it.
  • A bad scene can be talked through. Say so.
  • Character death happens. Bring a backup concept.
  • You are not competing with the other players.
  • Winning means surviving with the truth — not clearing a dungeon.
Before we roll

What you need

Dice

Percentile dice (d100) and a few d6s / d4s for damage — or the Compendium’s tabletop roller.

A sheet

Occupation, skills, Sanity, Luck, Hit Points. Create one here or copy a public pregen.

A reason to look

Why this case? A missing friend, a newspaper tip, a client who pays in secrets.

Primary job: uncover what is wrong and stop what you can. Secondary: keep each other alive and sane enough to finish the story.

Next briefing

Open Temporal Solutions

Same system. A campaign where modern civilians wake in the past
and Ambrosia puts them to work against the Mythos.

Continue to the setting primer →

The case file is open

Game on.

Pick an investigator. Name the question you’ll chase.
Leave the porch light on — and do not read the last page first.

Drawn from Call of Cthulhu 7th Edition (Chaosium). Setting & Mythos © Chaosium Inc. For personal table use.

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