Call of Cthulhu Game Guide

Posted by Andrew E. on

Summoning the Old Gods for Fun and Profit  

Call of Cthulhu has been lurking on game shelves for over 30 years and the game itself has always been a bit like an eldritch horror with a reputation for dense and mind shattering rules. Now with the onset of 7th edition we finally have a Cthulhu game that our mortal minds can comprehend and I’m happy to say the system has become pretty easy to pick up and learn. If you’ve been itching to delve into dark mysteries and learn knowledge that man should never have trifled with, now’s the time. Grab your revolver and your tome of arcane mythos as we blur the lines of reality and go through everything you need to know. 

What’s A Cthulhu?

Nerd culture has soaked up Lovecraftian horror like a sponge but if you’re still blessedly ignorant allow me to open your eyes to the terrible truth. Fundamentally, Cthulhu lore (or the “mythos”) all stems from the works of H.P. Lovecraft. Lovecraft was a little-known horror and science-fiction writer from the turn of the 20th century (with some rather regrettable racial views) who garnered a massive following long after his death. While never truly linked in any sort of continuity, his works and lore centered around “the old ones” and other mysterious entities have been combined into one sweeping world in which humanity is under constant threat and matters very little.

The famous Cthulhu is really just one member of a veritable rogue’s gallery of titanic alien creatures that exist in defiance of our limited understanding of the universe. There are creatures who ruled the world long before we arrived and may rule it again. There are creatures so utterly bizarre and powerful that we barely register as alive to them, and to most of them, we simply don’t matter.

The core of Cthulhu mythos and Lovecraftian lore is a very unique form of horror. Not only are there monsters, but the monsters are superior to us in every way. Not only is the world as we know it likely to come to an end, but the things destroying us are utterly disinterested in us and will end civilization like we would step on an anthill. Lovecraftian horror is about discovering just how small and insignificant we are, how little we actually know about reality. And when we finally touch just a piece of that real and fundamental truth, the knowledge drives us insane.

What’s Call of Cthulhu Like?

Narrative Gameplay

Thankfully, 7th edition Call of Cthulhu has slimmed down immensely. Earlier editions had a well-earned reputation for being impossibly difficult to play and needlessly complex, there was even an entire section about doing your character’s taxes! 7th edition has taken the opposite approach and now the system is honestly rules-light. Call of Cthulhu has become a primarily narrative driven game that relies on both the DM (keeper) and the players (investigators) to develop the story and uses dice rolls and hard rules as a last resort. Some of the lingering complexity remains, but most of it is locked behind “optional rules” that the keeper may or may not want to include.

None of this is exactly bad or good, but it is a style of TTRPG that you may be unfamiliar with if you’re used to just D&D or Pathfinder. Call of Cthulhu is a Roleplaying game, with the actual game part taking a backseat to the mystery.

For players this means that there aren’t really builds or strategies to speak of beyond being creative in the moment with whatever resources you happen to have. For example, you might think of throwing sand into the cultist’s eyes to blind them momentarily and give your character a chance to escape. There’s no “sand attack” on your sheet, it’s simply an idea that makes sense and your Keeper will have to decide what type of check you’ll need to roll, and what penalty to impose if you succeed.

For DM’s (Keepers) narrative gameplay can be simultaneously liberating and daunting. While you won’t be stuck digging through rulebooks for answers you will also be expected to make a lot of judgment calls on the spot. There’s very little dice rolling involved in this system, and for the most part it’ll be up to you to simply explain the outcomes of your player’s actions. This gives you immense freedom to craft the story you want to tell, at the cost of relying heavily on your personal creativity and quick thinking.

Lovecraftian Horror

If you come into Call of Cthulhu and try to play it like D&D with more fish monsters, you’re going to have a bad time. This system is designed for a horror setting, and all the monster and character abilities reflect that. The combat systems are very simple and rely on narrative description and there’s no classes or real character powers to speak of. The game wants to spend the majority of gameplay investigating a mystery, slowly learning the horrible truth, and more often than not simply running in terror when the threat is finally uncovered. If you try to run it like a “monster of the week” battling system, you’ll find it blatantly unfair and rather bland. It’s in the subtle hints and creeping suspicions that Call of Cthulhu really shines. The horror genre isn’t the same as an adventure genre with spookier monsters and treating this system like an adventure game will likely just get all the players killed.

Lethal Gameplay

Player characters in Call of Cthulhu won’t have a good life expectancy regardless of how benevolent or cruel their DM is. Even the weakest eldritch creatures around will likely take an investigator or two out with them and most monster entries are leagues beyond any thought of simply “taking them on”. In Call of Cthulhu players shouldn’t get too attached to their characters, and it’s rare to see an individual investigator survive through multiple adventures. Even those that do survive will likely be forever scarred both physically and mentally, rotting away in insane asylums or too traumatized from their near-death encounters to ever delve into the occult again. Horror is not a genre ripe with happy endings.

There’s nothing wrong with this style of gameplay, especially since character creation is far easier in this edition, but everyone involved needs to adjust their expectations. Beloved player characters may last only a couple play sessions. Keepers should either plan for short campaigns or have an easy way to bring new investigators into the game. Players should keep a few backup investigators rolled up just in case the next adventure proves to be too much for their current character.   

What Books Do I Need?

There are two “core” books that your playgroup will need for playing Call of Cthulhu, the Keeper Rulebook and the Investigator Handbook. As their names would imply, the Keeper needs the Keeper Rulebook and the Investigators will need the Investigator Handbook. Technically you can get by with just the Keeper Rulebook, but you’ll miss out on most of the investigator options so between the playgroup you should really have one of each.

Alternatively you could also get their Call of Cthulhu Starter Kit for way cheaper which has quick start core rules alongside 4 short adventures to enjoy and explore the system. This is a great option if your playgroup wants to test the eldritch waters before fully plunging in with a bunch of expensive books.

Optional Books

Pulp Cthulhu takes everything I said about weak investigators and a high mortality rate and throws it out the window. Pulp turns the game from horror to horror adventure, the stakes are still high, but the investigators are given a fighting chance with expanded options and abilities. It shifts the gameplay expectations away from fleeing the horror towards actually fighting the horror with some expectation of victory. This is the book you’ll need if you were wanting to run Call of Cthulhu more like a D&D game. 

Malleus Monstrorum Vol 1 and 2 are the “monster manuals” of the system. Volume 1 focuses on more minions and creatures the players have a chance against, while Volume 2 focuses more on the elder gods and their machinations. Think of Volume 1 as a book of monsters, and Volume 2 as a book of BBEGs to use as primary villains for your adventures. The Keeper Rulebook already contains a good retinue of horrors for your investigators to face so you don’t actually need these. I do recommend you pick them up once your playgroup has been regularly playing Call of Cthulhu for a while as they’ll add a ton of variety and spice to your encounters.

The “Alone Against” series consists of several Call of Cthulhu adventures that are designed for play alone and without a keeper. They’re heavily modified from the core game, but allow you to experience cosmic horror while completely isolated and ideally in a dark room… All in all I don’t rate this style of gameplay nearly as highly as the group experience, but if you find yourself without a playgroup these can make an excellent substitute and are a fun and terrifying way to spend an evening.

Setting Books

From the core books, Call of Cthulhu is set primarily within 1920’s America or England with the optional rules needed to play from the 1920’s all the way through to the modern era. And while you would be right in thinking Call of Cthulhu is a setting all its own, they’ve expanded your possibilities between several radically different flavors of eldritch horror.

Down Darker Trails takes the Cthulhu mythos and liberally mixes it with the wild west, cowboys and outlaws confront eldritch horrors on the American frontier. This is probably the most popular side setting for Call of Cthulhu, and it has already got a couple excellent adventure paths under its belt. I do really recommend you play this alongside the Pulp Cthulhu expansion though, as the setting really lends itself to more of a “horror adventure” experience, rather than pure cosmic horror.   

Call of Cthulhu Berlin remains in the 1920’s but shifts over to the chilly metropolis before it’s transition to soviet power. “Berlin” is probably the most straightforward setting change as it simply shifts location from the standard fare. It does have extremely detailed maps, NPCs, and plot hooks all working together to form a cohesive world in which to battle the eternal dark. This is a great option if you want to do some long-form campaigns in Call of Cthulhu and want most of the work done for you but would rather create your own adventure rather than follow an adventure path.

Cthulhu Dark Ages takes us back to the titular dark ages and lets you fight the eldritch powers as valorous knights, savage Vikings, and paganistic druids. This overhauls some of the core systems and makes them function better in the low-tech brutal times of the dark ages as humanity has even less chance to fight back the horror with sword and shield than they did with firearms. This is another one I really recommend playing alongside Pulp Cthulhu as the classical themes tend to put players more in mind of D&D than a period piece.  

Harlem Unbound stays within the 1920’s of the core setting but pins our focus to New York and specifically Harlem during the roaring 20’s amidst prohibition, gangsters, bootlegging and everything else that drew people’s attention away from the horrors lurking in the dark. More than other setting books Harlem Unbound tries to expand upon the investigators and their lives, it puts emphasis on the players as people trying to keep their lives from falling apart with something to actually fight for. I recommend this setting if you’re looking for a noir roleplaying experience set in the 20’s, and just also want to sprinkle in some eldritch terror. 

Core Mechanics

Call of Cthulhu is a d100 system, which means when you do things and need to check for success, you’ll be rolling a pair of d10’s commonly called percentile dice.

Percentile Dice consist of a 10’s place d10 and a 1’s place d10 which when rolled together give you a result between 1 and 100 (double zeros counts as 100). 

They’re used far less commonly, but you’ll also need the rest of the common “polyhedral” dice for a few things, meaning you’ll need at least 1 d4, d6, d8, and d20.

For the most part though, both the investigators and the keeper will be rolling percentile dice whenever they need to determine the outcome of an action, with the keeper only rolling rarely when players need to roll opposed checks against NPCs.

Each investigator has 8 characteristics that describe their characters and dictate how strong/fast/smart they are, Etc. They’ll also have any number of skills that detail how well they’ll perform at certain actions.

In both characteristic checks and skill checks, the investigator will roll percentile dice to determine if they succeed. Players succeed on checks by rolling lower than their skill or characteristic, or even lower if the check is particularly difficult. The difficulty of any given action is determined by the Keeper, and comes in 3 categories: regular (full skill), hard (half skill), and extreme (⅕ skill). 

For example:

Let’s say our investigator has a 50% jump skill level.

Now let’s say our investigator is being chased by eldritch horrors and needs to jump an 8-foot wide chasm to escape. The Keeper decides that this would be a regular jump check, and that if the investigator fails, he’ll fall into the pit. Because it is a regular check, our investigator simply needs to roll equal to or under his jump skill to succeed. He’ll roll percentile dice, and on a result of 50 or lower he’ll succeed on his jump, if he rolls above 50, he’ll fall.

Let’s change this example up and say the chasm is now 12-feet wide. The Keeper decides that this would be a hard jump check. Now because it is a hard check, our investigator must roll equal to or under half his skill to succeed. He’ll roll percentile dice, and on a result of 25 or lower he’ll succeed on his jump, if he rolls above 25, he’ll fall.

Now let’s make this challenge even more difficult by having him attempt this jump in the pouring rain, with broken glasses and a missing boot. The Keeper rightly decides that this would be an extreme jump check. Now because it is an extreme check, our investigator must roll equal to or under of his skill to succeed. He’ll roll percentile dice, and on a result of 10 or lower he’ll succeed on his jump, if he rolls above 10, he’ll fall.

Almost everything in Call of Cthulhu works off this system, and it conveniently only involves a single dice roll, and while the half and ⅕ seems a bit complicated, that’s math you’ll only have to do once and simply keep written down on your sheets. Most of the time you’re only making a single roll and are simply trying to roll under a value already written down.  

Creating a Call of Cthulhu Character

I remember back in earlier editions when this was a daunting task, but nowadays it’s a simple endeavor and should only take you 15-20 minutes.

Step 1: Characteristics

First we need to determine how your Keeper is determining characteristics, we’ll only go through the main “normal” method, but there’s a bunch of other ways including point buy options or standard arrays that your Keeper may decide to use instead.

There are 9 characteristics you’ll need to figure out, and they’re all rolled up a bit differently. The 9 characteristics are STR (strength), CON (constitution), SIZ (size), DEX (dexterity), APP (appearance), INT (intelligence), POW (power), EDU (education), and Luck.

Strength is pretty self explanatory and shows what your investigator is working with in the muscle department. Find your STR by rolling 3d6 and multiplying by 5.

Constitution represents your investigator’s overall health and resistance. Find your CON by rolling 3d6 and multiplying by 5.

Size is an averaged score showing your height, weight, and overall bulk. It’s important for your hit points, your ability to fit into small spaces, and can apply bonuses or penalties to your fighting abilities. Find your SIZ by rolling 2d6+6 and multiplying by 5.

Dexterity determines how fast you can move and how well you can dodge incoming attacks. Find your DEX by rolling 3d6 and multiplying by 5.

Appearance combines how good you look with how smooth you talk and just generally how likable you are, which can be important for things like smooth-talking the police after a shootout with cultists. Find your APP by rolling 3d6 and multiplying by 5.

Intelligence measures how well you learn, your reasoning skills, and how well you’ll do when confronted with puzzles and mysteries. Find your INT by rolling 2d6+6 and multiplying by 5.

Power represents your willpower, your resistance against magic and the maddening forces of darkness, it directly affects your sanity and a character with a higher power can resist going mad longer. Find your POW by rolling 3d6 and multiplying by 5.

Education is the knowledge you’ve accumulated through study, as opposed to the raw thinking power of intelligence. Education is often important for determining your skill points and knowledge of obscure academia. Find your EDU by rolling 2d6+6 and multiplying by 5.

Luck is rolled when something may or may not happen that is completely outside of the investigator’s control and is only rolled when circumstances rely only on the odds. Find your Luck by rolling 3d6 and multiplying by 5.

Step 2: Age

Your character’s age actually makes a fair bit of difference in-game. Decide what age you’d like your character to be, then apply the following changes to your characteristics:

5 to 19: Deduct 5 points among STR and SIZ. Deduct 5 points from EDU. Roll twice to generate a Luck score and use the higher value.

20s or 30s: Make an improvement check for EDU.

40s: Make 2 improvement checks for EDU and deduct 5 points among STR, CON or DEX, and reduce APP by 5.

50s: Make 3 improvement checks for EDU and deduct 10 points among STR, CON or DEX, and reduce APP by 10.

60s: Make 4 improvement checks for EDU and deduct 20 points among STR, CON or DEX, and reduce APP by 15.

70s: Make 4 improvement checks for EDU and deduct 40 points among STR, CON or DEX, and reduce APP by 20.

80s: Make 4 improvement checks for EDU and deduct 80 points among STR, CON or DEX, and reduce APP by 25.

Basically, you’re usually going to make characters in their 20’s and 30’s, super young kids take a penalty to their physical and education stats, and in exchange they get to be super lucky. At age 40 and up you start trading physical stats for the chance at higher education (though strangely your 80’s are strictly worse than your 70’s).

You’re also probably wondering what the heck an improvement check is. To make an EDU improvement check, simply roll percentage dice. If the result is greater than your present EDU add 1D10 percentage points to your EDU characteristic (note that EDU cannot go above 99).

Step 3: Attributes

With your characteristics set, we can figure out a few important attributes from them.

Your Hit Points keep track of how much punishment you can take before dying (an important number to know). To find your hit points simply add your CON and SIZ together and dividing that total by 10 (round down). So, for example, an investigator with 70 CON and 49 SIZ would have a total of 11 hit points.

Your MOV (movement rate) determines how fast you can move in a turn. You can move 5 X your MOV in a single turn. You determine your MOV by comparing your STR and DEX to your SIZ, and it is further modified if you’re really old:

If both STR and DEX are each less than SIZ: MOV = 7

If either STR or DEX is equal to or greater than SIZ, or if all three are equal: MOV = 8

If both STR and DEX are each greater than SIZ: MOV = 9

If age is in the 40s: deduct 1 from MOV

If age is in the 50s: deduct 2 from MOV

If age is in the 60s: deduct 3 from MOV

If age is in the 70s: deduct 4 from MOV

If age is in the 80s: deduct 5 from MOV

Finally, you need to figure out your damage bonus and build. Basically, if you’re really small and weak you’ll have penalties for hand-to-hand combat and if you’re huge and beefy you’ll get bonuses. You’ll find both attributes by combining your STR and SIZ and comparing the total on the following table:

Damage Bonus and Build


Damage Bonus


2 - 64



65 - 84



85 - 124



125 - 164



165 - 204




Step 4: Occupation and Skills

The books separate these two steps, but you really need to consider them both at once. Your occupation is the closest thing to a “class” you’ll be getting. We don’t have nearly enough time to go through them all (there’s nearly 100 in the investigator’s handbook alone) but they did their best to cover any conceivable occupation you may think up for the period, or at least something equivalently close. Each occupation gives you a different set of, occupation skill points, occupation skills, a credit rating, and your suggested contacts.

Most occupations will give you a bunch of skill points to spend based on your education, but some may use your appearance or dexterity, or any other characteristic for that matter. 

These occupation skill points can only be spent on your occupation skills and serve to specialize your investigator and make them particularly good at a few things.

Your occupation will also give you a range for a special skill called a credit rating. The credit rating is 7th edition’s solution to the whole “paying your taxes” section from old editions and serves to cut out the micromanagement when it comes to money. Your credit rating is a skill, and you’ll have to spend your skill points on it like any other. But your credit rating isn’t used for skill checks, instead it determines how wealthy your investigator is, and what they can afford.

Let’s say my investigator’s occupation is an antique dealer, which as an occupation has a credit rating range from 30 - 50. This means I’m required to spend at least 30 of my occupation skill points on my credit rating, and the maximum I can spend is 50. 30 is well within the “average” credit rating level, while 50 barely breaks into the “wealthy” bracket. Rather than keep track of your finances for every little thing, the bracket of your credit rating determines your level of living, whether or not you’d own a car or a house, how much cash you’d have on hand, and if you don’t spend past a daily limit you don’t have to note down spending at all. If I took the minimum of 30 for my antique dealer’s credit rating, I could only spend up to $10 worth of 1920’s money before needing to mark it off my total. But if I bumped my credit rating all the way to 50, I could spend up to $50 old timey bucks each day without breaking a sweat.

And the last thing you gain from your occupation is your suggested contacts. These aren’t things you actually need to set up ahead of time, but you’re investigators, and investigators need to ask a lot of people a lot of questions. Say there’s eldritch trouble afoot with a suspicious circus in town. The acrobat occupation specifically lists circuses and carnivals under their suggested contacts, and your acrobat investigator may well have an in with the big top that gets the players past the tent flap where they would have been turned away otherwise.

Finally, you get an opportunity to round out your character with personal skills. Each investigator gains a number of personal skill points equal to their INT X 2. These points can go into any skill you feel like, even skills outside of your occupation.

Step 5: Equipment

This part is very simple considering how your credit rating works, and generally if your character should have something based on their occupation they just have it. No need to write every little thing down. You should note down however anything major that you think is important, like a car, or a special weapon you’re really attached to.

Step 6: Backstory

The books have extensive sections about this but fundamentally you’re free to create whatever elements you’d like with one major hiccup; the keeper can change your mind! You’ll be needing to fill in at least one each of beliefs, significant people, meaningful locations, treasured possessions, and traits. You get to select one of these as a sort of “core trait” but the rest can be freely messed with by the Keeper when your mind comes under assault, sometimes completely flipping an investigator’s personality!

Step 7: Halves and Fifths

The book expects you to do this earlier, but I find it easier to do once every other thing has been settled. The half and ⅕ values of your characteristics and skills are important for finding success for hard and extreme checks. It’s best to simply write all these values down ahead of time. If you’re using the official character sheets, you’ll find spaces for all of these values lined up for you already.

Bottom Line, Should I Play Call of Cthulhu?

Call of Cthulhu 7th edition is probably my favorite incarnation it has had over the decades. It’s fast, easy to get into, and it just glosses over the boring stuff that bogged down the earlier incarnations of the game. Make sure to adjust your expectations though. Call of Cthulhu is a horror game, and just how many horror movies can you name where everybody survives until the end? I find that the horror style gameplay lends itself very well to quick 1-3 session adventures where players won’t mind losing a character so much, and tends to falter with really long form campaigns where each individual player is likely to cycle through multiple investigators before the adventure is through. If you’re wanting to play longer adventures, try adding Pulp Cthulhu to the base rules for that extra survivability. Otherwise, keep your campaigns short, and have fun driving your playgroup to the brink of insanity!




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Last updated: January 27, 2019

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