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Joe Kenobi

A Guide to the Different Cthulhu Systems

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While I’ve been playing Call of Cthulhu for nearly a decade, I only recently made the jump to the online community, coinciding with my start GMing games. One thing that surprised me was the high volume of Cthulhu RPG variants and systems, only a few of which I’d previously been aware of. I did some looking around and couldn’t find a good guide differentiating between the different systems—so, inspired by klecser’s post, I decided to do the research to make one. Some of this is cribbed from Jalor218 on Reddit and Morgan on 21st Century Philosopher. Jalor218’s comment that he hadn’t played half the systems he summarized gave me the confidence to take a stab at something similar.

I've drawn attention to the most high-profile systems—the ones that I've seen referenced time and again online—by putting them in green. If I’ve misrepresented something or left out essential details, please let me know and I’ll be happy to revise this post. Additionally, if there's a prominent system I haven't included, let me know and I'll revise to add it.

I. Classic Call of Cthulhu and its near-variants:

Call of Cthulhu – Utilizes a d100 percentile dice system called the Basic Roleplaying System, or BRP. Scenarios are usually set in the 1920s. Call of Cthulhu is currently on its 7th Edition, though the rules are very similar and scenarios can be easily converted across editions. Call of Cthulhu focuses on investigation, leaves plenty of room for failure, and has lethal combat. Characters will usually die or go insane. The gamemaster is called the keeper and characters are called investigators.

Essential rulebook(s): Call of Cthulhu Keeper Rulebook, 7th Edition

Free resource: Call of Cthulhu 7th Edition Quick-Start Rules

There are several Call of Cthulhu modules that share an identical ruleset and gaming system to the usual Call of Cthulhu, but have special names to denote a special setting and a unique reference book to assist with roleplaying in that setting. These are:

Cthulhu Invictus – Set in Ancient Rome (circa 100 AD).

Essential rulebook(s): Cthulhu Invictus

Cthulhu Dark Ages – Set during the Dark Ages (circa 1000 AD).

Essential rulebook(s): Cthulhu Dark Ages

Down Darker Trails – Set in the American Old West (circa late 1800s).

Essential rulebook(s): Down Darker Trails

Cthulhu by Gaslight – Set in 1890s Victorian England.

Essential rulebook(s): Cthulhu by Gaslight

Achtung! Cthulhu – Set during World War II, with investigators playing Allied agents fighting the Secret War against the Nazi Black Sun.

Essential rulebook(s): Achtung! Cthulhu: Keeper's Guide to the Secret War

Cthulhu Now – Set in modern times.

Essential rulebook(s): Cthulhu Now

H.P. Lovecraft's Dreamlands – Set in H.P. Lovecraft's Dreamlands, where investigators travel down the seven hundred steps, through the Gates of Deeper Slumber, and into the realm of dreams. 

Essential rulebook(s): H.P. Lovecraft's Dreamlands 

Pulp Cthulhu – Utilizes a d100 BRP system similar to Call of Cthulhu, but with several unique rules. Scenarios are usually set in the 1930s. Pulp Cthulhu changes the game to turn the investigators into action heroes, similar to Indiana Jones, who are much less likely to die in combat and more equipped to fight the Cthulhu mythos directly. It has a pulpy, action/adventure tone.

Essential rulebook(s): Pulp Cthulhu

Trail of Cthulhu – Utilizes a mostly diceless points-based system (some limited use of d6) called the GUMSHOE System. Scenarios are usually set in the 1930s. The GUMSHOE System is designed for investigative roleplaying such that a failed dice roll cannot prevent the finding of a clue. Trail of Cthulhu emphasizes storytelling and interpreting clues, as opposed to roleplaying and gathering clues.

Essential rulebook(s): Trail of Cthulhu rulebook

Free resource: Trail of Cthulhu downloads and resources

Cthulhu Confidential – Trail of Cthulhu designed for play with one gamemaster and one player.

Essential rulebook(s): Cthulhu Confidential

Cthulhu City – Trail of Cthulhu set in a New England overrun by the Cthulhu Mythos.

Essential rulebook(s): Cthulhu City

Delta Green – Utilizes a d100 BRP system similar to Call of Cthulhu, but with several unique rules. Scenarios are usually set in the 1990s or modern times. Delta Green presents a scenario in which characters are government agents investigating and combatting mythos elements, similar to The X-Files. It takes the investigative tone of Call of Cthulhu and adds an air of conspiracy and secret societies. The gamemaster is called the handler and characters are called agents.

Essential rulebook(s): Delta Green: Agent’s Handbook

Free resource: Delta Green: Need to Know quick-start rulebook

The Fall of Delta Green – A Delta Green prequel that utilizes the mostly points-based GUMESHOE System used in Trail of Cthulhu. Scenarios are usually set in the 1960s.

Essential rulebook(s): The Fall of Delta Green

Dark Streets – Utilizes a d100 percentile dice system from Renaissance Deluxe, which takes its system from OpenQuest, which is based on BRP. Scenarios are set in 1750s London. Characters are members of London’s proto-police force. Dark Streets gameplay is very similar to traditional Call of Cthulhu, emphasizing investigation and deduction while keeping combat occasional and deadly.

Essential rulebook(s): Dark Streets 2nd Edition - Core Rulebook

Raiders of R’lyeh – Utilizes a d100 percentile dice system based on RuneQuest, a BRP system. Scenarios are set in 1900-1913. Characters are mercenary rogues exploring the frontiers of the known world. Closer to Pulp Cthulhu than traditional Call of Cthulhu, Raiders of R'lyeh looks to Robert E. Howard’s Mythos and Weird stories as an additional influence.

Essential rulebook(s): Raiders of R’lyeh: Gamemaster’s Guide & Complete Rules

GORE – Utilizes a d100 percentile dice system that is fairly rules-light and based on OpenQuest, which is based on BRP. GORE stands for Generic Old-school Roleplaying Engine, and is designed to allow Lovecraftian adventures in science fiction, fantasy, investigative, and classical horror settings.

Essential & free rulebook: GORE

 

II. Variants with a strong “rules-light” emphasis:

Cthulhu Dark – Utilizes a d6, rules-light system. Loosely related to Trail of Cthulhu, with an emphasis on storytelling and the how of things rather than the whether of things. Maintains a focus on cosmic horror within a barebones rules environment.

Essential rulebook(s): Cthulhu Dark hardcover rulebook

Free resource: Cthulhu Dark: A Rules-Light System for Lovecraftian Horror

Cthulhu Grey – Utilizes a d6, rules-light system closely based on Cthulhu Dark. Cthulhu Grey adds in a Harm stat, greater character differentiation, and rules for Magick.

Essential & free rulebook: Cthulhu Grey: A Cthulhu Dark Hack

Cthulhu Grim – Utilizes a d6, rules-light system closely based on Cthulhu Dark and Cthulhu Grey. Cthulhu Grim adopts rules specifically suited for campaign play.

Essential & free rulebook: Cthulhu Grim, based on Cthulhu Dark and Cthulhu Grey

Lovecraftesque – Utilizes a diceless, GMless system. Creates a GMless story of a lone character confronting cosmic horror in the form of a mystery that builds to a climax. Each playthrough will create a single one-shot scenario designed for completion in a single session. Players take on the roles of Narrator, Witness, and Watchers.

Essential rulebook(s): Lovecraftesque rulebook

Free resource: Lovecraftesque free references and handouts

De Profundis – Utilizes a diceless, GMless, correspondence-based system. Players take turns writing letters in-character to one another in the style of H.P. Lovecraft. Includes an option for solo play.

Essential rulebook(s): De Profundis Second Edition

The Cthulhu Hack – Utilizes dice of multiple sizes in a rules-light system called The Black Hack. As a rules-light system, The Cthulhu Hack emphasizes storytelling and offers player-focused gameplay designed for quick and easy pick-up play.

Essential rulebook(s): The Cthulhu Hack rulebook

Free-ish (PWYW) resource: The Cthulhu Hack: Quickstart

tremulus – Utilizes a d6 system that is fairly rules-light called Powered by the Apocalypse. tremulus is a storytelling-first game that requires limited prep and emphasizes investigation and survival.

Essential rulebook(s): tremulus rulebook

Cthulhu Abides – Utilizes a d6 “poker dice” system that is fairly rules-light and similar to a system called The Whispering Vault. Scenarios are generally set in 1920s Britain. Cthulhu Abides is designed to be heavier than Cthulhu Dark, with greater character differentiation, while still lighter than Call of Cthulhu and Trail of Cthulhu. Intended as a Pick Up & Play RPG.

Essential rulebook(s): Cthulhu Abides: A Roleplaying Game of Investigation & Madness

Free resource: Cthulhu Abides: A Roleplaying Game of Investigation & Madness (PDF)

Unnamable – Utilizes a d6, rules-light system. Unnamable greatly simplifies skill checks so that character descriptors, personality traits, and descriptions rather than ranked skills are used for skill checks. It also preserves character sanity to a greater degree than Cthulhu Dark.

Essential & free rulebook: Unnamable: A Little Lovecraft Game

Unspeakable – Utilizes a d6, rules-light system closely based on Unnamable. Unspeakable adds a bit more character differentiation as well as increases the risk of character insanity.

Essential rulebook(s): Curse of the Yellow Sign Collected

 

III. Adaptations intended to bring Cthulhu roleplaying into other RPG universes:

Call of Cthulhu d20 – Utilizes the d20-based system of Dungeons & Dragons, 3.5 edition. It was created to maintain the feel of the original Call of Cthulhu, but using a dice system that would be more familiar to Dungeons & Dragons players and which could allow for the porting of characters, monsters, and other content between the two universes. Currently out of print.

Essential rulebook(s): Call of Cthulhu d20 edition rulebook

Sandy Petersen's Cthulhu Mythos for 5E – Utilizes the d20-based system of Dungeons & Dragons, 5th edition. Sandy Peterson's Cthulhu Mythos is designed to allow Cthulhu roleplaying within the most recent implementation of the Dungeons & Dragons universe and system.

Essential rulebook(s): Sandy Petersen's Cthulhu Mythos (5E) + D&D Dungeon Master's Guide + D&D Monster Manual + D&D Player's Handbook

Sandy Petersen’s Cthulhu Mythos for Pathfinder – Utilizes the d20-based system of Pathfinder. Sandy Petersen’s Cthulhu Mythos is designed to allow Cthulhu roleplaying within the Pathfinder universe and system.

Essential rulebook(s): Sandy Petersen’s Cthulhu Mythos (PF) + Pathfinder Roleplaying Game Core Rulebook

World of Cthulhu – Utilizes the d10 system of World of Darkness called the Storyteller System. World of Cthulhu is designed to allow Cthulhu roleplaying within the World of Darkness universe and system.

Essential rulebook(s): World of Cthulhu: Lovecraftian Roleplay in the World of Darkness (free) + New World of Darkness Rulebook (1st edition)

Cthulhu Pulp: Tales from Beyond Pulp – Utilizes the d20 system of Pulp Adventure. Designed to allow Cthulhu roleplaying within the Pulp Adventure system, with a focus on using super-science and muscle to fight the forces of the Cthulhu Mythos. Out of print.

Essential rulebook(s): Pulp Adventure, Second Edition: Cthulhu Pulp: Tales from Beyond Pulp

 

IV. Other variant systems:

Cthulhu Live – Utilizes a points-based live action roleplaying (LARP) system with no randomizer. Aims to stay true to the feel of Call of Cthulhu, where investigators are flesh-and-blood humans and violence is consequential.

Essential rulebook(s): Cthulhu Live 3rd Edition (LARP)

Realms of Cthulhu – Utilizes dice of multiple sizes in a fairly rules-light system called Savage Worlds. Realms of Cthulhu remains investigative in nature but incorporates a faster pace and more action, along with the addition of Combat Magic.

Essential rulebook(s): Realms of Cthulhu rulebook + Savage Worlds Adventure Edition

Shadows of Cthulhu – Utilizes a d20 system called True20. Scenarios are usually set in the 1920s. Shadows of Cthulhu presents an experience similar to Call of Cthulhu d20, but with a higher degree of action/pulp and while utilizing the True20 system, intended to provide a d20-based system that requires no other kinds of dice and minimizes the need for tracking things like hit points.

Essential rulebook(s): Shadows of Cthulhu + True20 Adventure Roleplaying, Revised Edition

Nemesis– Utilizes a d10 dice-pool system called One-Roll Engine. Nemesis focuses on dark horror inspired by Lovecraftian themes and utilizes a Madness Meter to simulate insanity and mental trauma.

Free & essential rulebook: Nemesis: Roleplaying in Worlds of Horror

 

V. Cthulhu-adjacent games with their own unique tone:

Cthulhu Risus – Utilizes a d6, rules-light system called Risus. Cthulhu Risus offers a fast-paced and humorous take on Lovecraftian horror.

Essential & free rulebook: Cthulhu Risus

CthulhuTech – Utilizes a d10 dice pool “poker dice” system called Framewerk. Scenarios are set during the Aeon War in 2085. CthulhuTech blends Lovecraftian horror with anime-style mecha, sci-fi, and magic. For mature audiences only.

Essential rulebook(s): CthulhuTech Core Book

Free resource: CthulhuTech V2: The Shadow War Open Beta

Cthulhu for President – Utilizes a d6 system called the BEER Engine. Cthulhu for President offers tongue-in-cheek humor as players take on the role of Elder Party staffers in an attempt to get their Great Old One elected.

Essential rulebook(s): Cthulhu for President: The Game

Fantasy Cthulhu – Utilizes the custom dice (d6) system of FATE. Fantasy Cthulhu places the Cthulhu mythos within a fantasy setting powered by the FATE system.

Essential rulebook(s): Fantasy Cthulhu powered by FATE Core

Post-Cthulhu – Utilizes a custom dice (d6) system called FATE. Scenarios are set in the future, after Cthulhu has risen. Players take on the role of survivors of the Cataclysm who wander a post-apocalyptic landscape stalked by Lovecraftian monsters.

Essential rulebook(s): Post-Cthulhu

FATE of Cthulhu – Utilizes a custom dice (d6) system called FATE. Scenarios are set in the present day, with characters who are time-travelers from a dark future in which the Great Old Ones have returned. FATE of Cthulhu sets Lovecraftian horror against a Terminator-like backdrop. Currently on Kickstarter.

Essential rulebook(s): On Kickstarter now

Edited by Joe Kenobi
Updated to add Nemesis & Sandy Petersen's Cthulhu Mythos for 5E
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I love this topic. I am always looking for new lovecraftian games that could inspire me. Some games that I know, beyond the listed, it is:

Realms of Cthulhu: a Savage World setting. I'm not into Savage Worlds, so I don't have much to say, but so much people have good things to say about this setting so I'm curious about it.

Here there are some reviews: https://www.goodreads.com/book/show/7434203-realms-of-cthulhu

Tremulus: a Apocalypse World Engine game. The system is knowing by its tools for improvised stories. There are playbooks, that work's as occupations. Each one of them has its own movies. Movies are something like the types of action that a player could do with that character.

Font: https://www.kickstarter.com/projects/1227949612/tremulus-a-storytelling-game-of-lovecraftian-horro

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Great post, good to have all of your option under one thread.

Cthulhu Invictus recently got updated to 7th edition via kickstarter: Full list of product here.

Cthulhu Invictus (new) Corebook

Obviously,  the rules were updated but there was also some cleaning up and it has a great selection of archetypes both for Romans and Non-Romans.

Edited by André Roy

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Surprisingly, Risus.  It’s an ultra simple system intended for off the cuff silly games — but a large portion of the fan-made campaigns are Cthulhu.

 

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Thanks, all. I've revised the original post to add in entries for each of the systems you mentioned.

Obviously, it will be near-impossible to include every form of Cthulhu roleplaying in a single message board post, but I'm hopeful I can maintain this list to accurately capture prominent systems that newer Cthulhu roleplayers might come across mention of.

There are many systems on this list that I've never touched, so if I've misrepresented any, do let me know and I'll happily revise. I've also attempted to keep the main post neutral in tone and free of any value comparisons between the systems, but if you have systems you particularly like or dislike, I'd think this thread could be a useful place to promote their adoption or discourage their use.

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Nice topic!

I don't know if those qualify, maybe under the "Trail of Cthulhu" banner (similarly to the ones like Cthulhu Invictus under CoC? )

  • Cthulhu Confidential: modified Gumshoe rules for playing with only 1 GM and 1 player.
  • Cthulhu City: an alternate setting for Trail of Cthulhu where the Mythos seems to have completely taken over the coast of New England.
Edited by lordabdul

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Thanks, all. I've added in the latest suggestions while also reorganizing the list into a few categories in hopes of keeping things from growing too unwieldy.

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John Wick's Curse of the Yellow Sign (at least the version he kickstarted) came with the Unspeakable system and you could play using that or CoC.

You have (or had) Cthulhu Live for LARPers.  Which had a fair bit of support.

Also you have Cthulhu For President (the BEER Engine) - although I don't know if anyone has actually played that.

I am not sure if you want to mention PDQ - Three Kings - the Achtung Cthulhu scenario came in a PDQ version (as well as CoC, Savage Worlds and I think FATE) but nothing else in that line, including the other adventures in that campaign, ever did AFAIK.

Which comes to Fate. We do have FATE of Cthulhu coming out. But there was a game called Post-Cthulhu (published by Starbright Illustrations in 2016) which was a FATE Core game - I haven't seen it but it seems to be set after Cthulhu has risen. The same company also published Fantasy Cthulhu which involved a traditional fantasy setting being invaded by the usual Lovecraftian creatures and gods (also using FATE Core).

Another game which I haven't seen is Cthulhu Abides by Jonathan Rowe which was self-published I think. There was also  Cthulhu Pulp: Tales From Beyond Pulp for the Pulp Adventure RPG.

If you are including free web published games (like Cthulhu Risus) you can also add in Cthulhu Grey and Cthulhu Grim.  There was also World of Cthulhu for Worlds of Darkness.

   

 

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One correction. With the latest edition of Dark Streets (2nd edition) you no longer need the Renaissance book.

Edited by rsanford

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I've updated the Dark Streets link--thanks for flagging, @rsanford.

I'll try to look into the others and get them added, described, and categorized within the next week or so.

2 hours ago, seneschal said:

The list keeps getting longer and longer.  Um, you investigators better get busy.  It looks as if the Mythos is winning.  😱

I'll admit, it's turning into more of an undertaking than I anticipated! I expected there would be a small handful of systems I'd missed that would be notable enough to revise and include. We're already at 19 suggested additions--and it hasn't even been three days since the initial post!

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On Realms of Cthulhu I think you also need the Savage Worlds core rules (and there are a number of different varieties of those) as well. But my copy of the rulebook is buried in a pile of others and not to hand.

Another game that might be mentioned is De Profundis - which is a strange beast, it is GMless and epistolary, but definitely fits as a Lovecraftian game.

Also The Laundry by Cubicle 7 is obviously based in the Mythos (as the early novels were) and uses the BRP system.

Finally Achtung! Cthulhu is being republished (2nd edition?) using Modiphius's 2d20 sytems. A beta version is available to playtesters.

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This should be placed under the "I. Classic Call of Cthulhu and its near-variants:" section under "Call of Cthulhu" 

H.P. Lovecraft's Dreamlands  - Set in H.P Lovecraft's Dreamlands, where investigators travel down the seven hundred steps, through the Gates of Deeper Slumber, and into the realm of dreams.

Essential Rulebook(s): H.P. Lovecraft's Dreamlands

 

 

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Thanks, @measuredrums! Not sure how I overlooked Dreamlands. I appreciate you putting it in a matching format I could easily drop into the main post!

I'm still working on compiling the others and should have a batch edit ready to go in soon--possibly later tonight, most likely in the next day or two. @andyl, I can't find any info on World of Cthulhu. Do you have a link/resource I could reference?

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*pant, pant*

Okay, edits are made! I also did some slight rearranging.

The Laundry is right on the bubble for me, since it's not technically a Cthulhu RPG, but rather an RPG based on a book series with clear Mythos elements. The fact that it's currently unavailable and being revamped tipped the scales so that I'm not going to include it.

Since the 2d20 Achtung! Cthulhu implementation is in beta and not in wide release yet, I'm going to leave that off for the time being, too.

Nemesis is a tough one, because while it contains some Cthulhu Mythos elements and Lovecraftian influence, it looks like it's designed to be more of a general horror RPG, with several horror influences. I'd like to keep this list focused on Cthulhu roleplaying--I'm a big fan of Dread as a horror RPG, for instance, but haven't included it because I don't think it belongs here. I'm going to leave Nemesis off, too, unless someone who's played it argues that its central conceit is in fact Lovecraftian.

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4 hours ago, Joe Kenobi said:
I'm going to leave Nemesis off, too, unless someone who's played it argues that its central conceit is in fact Lovecraftian. 
 

How about someone who wrote for it? The spells are straight out of Lovecraft, because that's what I used. Dan Harms wrote the monsters. Dennis Detwiller, Greg Stolze and Shane Ivey of Delta Green fame wrote everything else. Plus the DTRPG blurb says:

"NEMESIS: Roleplaying in Worlds of Horror is a free game using the One Roll Engine (also seen in Godlike, Wild Talents, Monsters and Other Childish Things, Reign, and A Dirty World) for modern-day horror, particularly the Lovecraftian horror of the Cthulhu Mythos."

 

Also, there is a D&D 5e version of Sandy Petersen's Cthulhu Mythos. I think it is superior to the Pathfinder version. YMMV of course.

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5 hours ago, Gundamentalist said:

How about someone who wrote for it? The spells are straight out of Lovecraft, because that's what I used. Dan Harms wrote the monsters. Dennis Detwiller, Greg Stolze and Shane Ivey of Delta Green fame wrote everything else. Plus the DTRPG blurb says:

"NEMESIS: Roleplaying in Worlds of Horror is a free game using the One Roll Engine (also seen in Godlike, Wild Talents, Monsters and Other Childish Things, Reign, and A Dirty World) for modern-day horror, particularly the Lovecraftian horror of the Cthulhu Mythos."

 

Also, there is a D&D 5e version of Sandy Petersen's Cthulhu Mythos. I think it is superior to the Pathfinder version. YMMV of course.

Totally valid. I just don't have personal experience with it so wanted to make sure I wasn't wandering too far afield--on your insight, I've now included it above.

Also added in the Sandy Petersen's Cthulhu Mythos for 5th edition. Thanks for flagging it!

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