A first run of Call of Cthulhu at the table

To run Call of Cthulhu you need the rules, a short scenario, a set of ready-made investigators and one evening. Chaosium publishes the Quick-Start Rules as a free PDF, and they carry everything a first session needs: the percentile system, the Sanity rules, four pregenerated investigators, and The Haunting, a scenario set in 1920s Boston. Read the scenario twice, work out how each clue reaches the table, and let the dice handle the rest.

The rest of this is about the chair you are sitting in. The mechanics are small and they are learnable in twenty minutes. The habits that make a session work are the part nobody hands you in a book.

The Keeper's job

The Quick-Start Rules give the game moderator a title: Keeper of Arcane Lore, Keeper for short. The job is to run the game for the other players and apply the rules where they are needed. Everyone else plays an Investigator of the Unknown, an ordinary person in over their head.

That job description is doing more work than it looks. "Where they are needed" is the whole craft. A Keeper who calls for a roll every time somebody opens a drawer turns a two-hour investigation into a dice-rolling contest, and the dread drains out through the floor. Ask for a roll when failure would change what happens next. An accountant reads a ledger. A doctor recognises a wound. Narrate those and move on.

The four grades of success

Every roll is a d100 against a skill or characteristic value, and the result has four grades: a failure, a regular success, a hard success, and an extreme success. A hard success needs half the value or less, so an investigator with STR 60 needs 30 or below. Opposed rolls compare grades, with a hard success beating a regular one, and a tie going to the higher skill value.

Set the difficulty before the player rolls, out loud, and say what it means. "Give me a Library Use roll, and a hard success gets you the second document as well" tells the table what is at stake in one sentence. Announcing the grade afterwards, once you have seen the number, teaches players that the target moves, and they stop trusting the dice.

The pushed roll

A failed roll is not always the end of an attempt. The Quick-Start Rules let a player push a roll, trying a second time with the stakes raised, and if the pushed roll fails, you inflict a dire consequence rather than another shrug. The rules also give you the option of foreshadowing what that consequence might be before the player commits.

Use that option every time at a new table. Say it plainly: try the crypt door again and you can bring the spade, but if it goes wrong the noise brings somebody. Now the player is making a decision instead of asking for a second chance, and the failure that follows is theirs.

The pushed roll also solves the problem every new Keeper hits, which is the investigation that stops dead because one roll failed. It is a release valve, and it is better than the alternative fix of inventing a clue on the spot, because the price is stated up front.

Bonus and penalty dice

Where conditions help or hinder, the Quick-Start Rules add a bonus or penalty die: an extra tens die rolled alongside the usual percentile pair, taking the better or the worse result. One bonus die and one penalty die cancel each other out.

This is the tool to reach for instead of refusing an action. A player wants to talk their way past a hostile desk sergeant with no relevant skill and a bad plan, so give the roll a penalty die and let them try. Saying no ends a scene. A penalty die keeps the scene and prices the decision.

Sanity as the pacing dial

Sanity is what this game spends instead of hit points. Losses are written as a pair, in the shape 0/1D6 or 2/1D10. The first number applies when the roll comes in equal to or under the investigator's current Sanity, the second when it goes over. Lose 5 or more points from a single Sanity roll and the investigator has taken major emotional trauma, which sends the player to a 1D100 roll.

There is one rule here that new Keepers keep leaving on the page: when a Sanity roll fails, you get to dictate the investigator's next action while the fear has hold. They scream, they freeze, they pull the trigger. Take it. It is the moment the horror stops being described and starts happening to somebody, and a player will remember the sentence you said far longer than the number they rolled.

Pace the losses. A scenario that drains everyone in the first scene has nowhere to go by the third. Ask for the roll first, look at the result, then describe what that particular investigator perceives. The one who held together sees a shape in the water. The one who did not sees all of it.

Prep for one evening

1. Read the Quick-Start Rules end to end. It takes under an hour and covers everything the first session uses.
2. Read The Haunting twice. The first pass is the plot, the second is the clue chain, and the second is the one that matters.
3. Write the clue chain on one sheet: which clue sits in which room, which skill uncovers it, and what the players learn if every roll fails. Give each necessary clue two routes in.
4. Print the four ready-made investigators and let players pick. Names and genders are theirs to decide, and that is the whole of character creation for tonight.
5. Decide your rolling convention before play. Say when you want a roll, name the difficulty first, and stick to it.
6. Set a stopping point. An investigation ends well on a discovery, badly on a corridor.

Step three is the one that saves the evening. Gatekeeping a required clue behind a single roll is the most common way a first session stalls, and it stalls because of a prep decision rather than anything a player did.

After the first scenario

Call of Cthulhu was originally written by Sandy Petersen, revised later by Lynn Willis and others, and the seventh edition was written by Mike Mason and Paul Fricker. It has been in print since 1981, so the scenario shelf behind it is deep, and Chaosium's own getting started page points new Keepers at the Starter Set next.

There is also a wide supply of scenarios from players. The Miskatonic Repository lets anyone with a DriveThruRPG customer account publish their own Call of Cthulhu material, with no publisher account and no extra licence, on a 50/50 split of profits, and plenty of it is free or pay what you want. Quality varies and prices are low, which makes it a cheap place to find a one-shot for an evening you did not plan for.

Run the short scenario, keep the clue chain honest, and hand the fear to the players one failed Sanity roll at a time.