Cosmic Horror Mindset


Hey folks,

I’m neck-deep into cosmic horror / Call-of-Cthulhu-style gameplay with my ICRPG table group. Hence I’m overhauling my overall GM mindset. I’d like to build a thread with you guys to help each other out with getting into the mindset.

What are your (system neutral) tips GMing cosmic horror / CoC style games?
(I’d like to keep them independent from rules and mechanics.)

My approach is

  • 100% Theater of the Mind (it wasn’t as hard as I thought, although my table origins at heavy use of terrain)
  • More scene descriptions (introducing more human senses: see, smell, hear, feel, taste)
  • More NPC descriptions (to fuel ToTM even more)
  • Still sitting on bullet lists in my journal spread

What I’m struggling with (= for what I’d like to ask you about)

  • Structuring the game prep (Room structure isn’t working here imho, and I want to “break free” from linear adventure design, too).
  • Keeping things tight in the journal (I don’t want more than two facing pages).
  • Without sacrificing content depth (sure improv is necessary, but some things need to be build upfront)
  • (Re-)Introducing 3 Ts into my games (since thing’s are less combat-heavy and less “fantasy-ish”, I’m struggling with it).

Here are some specific questions:

  1. How do you prep such games? Where do you start? Some “what happened here before”-stuff or more like “what needs to be done”?
  2. How do you organize your prep? Scenes? Locations? Adventure phases?
  3. How do you keep things tight without sacrificing depth? How to avoid writing smaller and smaller to fit things it :smiley:
  4. How do you handle the Runehammer revelations (trap design, 3Ts, 3Ds, DEW) without pushing things into pulp territory?



Why are you saying that room design doesn’t work here? I mean sure the words Timer, Treat, Threat are not immediately evocative of an horror room, but if you’ve played Alien Isolation Treats become hiding places, Threats become ringing bells (to draw in the monster), and the timer is how long the players have to navigate to the next room before they get caught!

Do as usual: draw index cards for your structure. Confine your players then arrange for them to meet your monsters in a safe environment to telegraph how deadly he is. Perhaps mark the index cards upon which you want your players to be challenged by your monster directly. You don’t need to rethink the loot, if it’s useless against the horror monster they will have to learn to use it creatively.

For your specific questions:

  1. “What has happened here before” is usually how I go about everything now. Keep it short and sweet. Answer the five Ws. It’s often enough to help you let the players discover what has happened by themselves and for you to adjudicate without needing to add additional stuff.
  2. In Dungeon World, I think, I’m not sure, it just asks you to set down a bullet point list of three things that you want to describe. A single word or half a sentence will do. This will also save you space.
  3. See point 1! :smile:
  4. I don’t know what you’re talking about!

Last point: Human senses are good, but in a horror story I think those are only good to focus upon to enhance the emotion you’re trying to make them feel. Which depends on the type of horror you’re going for, of course. As such, perhaps focus more on the emotions: NPCs become useful to share their feeling of dread, fear, and despair. I hope this helps! GLHF! :muscle:


Greetings, glocke:

I have homebrewed and run a lot of Call of Cthulhu cosmic horror adventures, so I hope my thoughts, experiences, and perspectives can be of some use to you as you examine and refine your own gamemaster strategies for running investigative cosmic horror RPG sessions.

Conventional mystery stories are the most highly structured narratives in all of genre fiction—just ask anyone who has every had to write one, tried to write one, or wanted to write one. The stories are typically structured into four acts rather than three with upwards of a dozen identifiable stylized plot beats (sometimes as many as 28(!), depending upon what standard compositional template you follow). The archetypal structured mystery story is the ubiquitous murder mystery, which when viewed most simply can be organized around the timed drop of “the three corpses”—the inciting incident for the investigation, the redirecting setback, and the revelation that locks the protagonist and antagonist in a climactic battle—and the events circumstances surrounding their demise.

Unless you’re running a Cthulhu funhouse dungeon full of overwhelming Mythos monsters popping out of the shadows to eviscerate your underpowered player characters one by one without warning, your cosmic horror RPG adventure will be primarily investigative in nature, and the story narrative you present to your players to explore will have much in common with traditional mystery investigation fiction in terms of its organization and structure. The bad news is that there usually needs to be many more moving parts that the GM needs to track and advance than in the typical ICRPG heroic fantasy quest, requiring greater planning, precision, and attention to detail for the adventure’s narrative to hold together. The good news is that even though the GM has a lot of prescribed responsibilities behind the scenes in an evolving mystery story, to the players your RPG mystery investigation can still feel like a complete sandbox if you do your part. The other good news is that you can still have Mythos monsters pop out to overwhelm and eviscerate your PCs.

I realize that the ICRPG community favors strongly a “less is more” bullet-points-only approach to preparing very straightforward “timer-threat-treat-GO!” encounters and adventures, but for the reasons mentioned previously, putting a little more thought, effort, and planning into your cosmic horror adventure will pay big dividends at the table. With the addition of some simple genre-specific mechanics and tropes, ICRPG is an excellent engine that supports cosmic horror roleplay quite well, and its streamlined mechanics and general ease of use for GMs designing playable content will help you create space within your allotted prep time to pay attention to the needs of your investigative narrative. If you lean into some of the the similarities your cosmic horror adventure shares with mystery fiction, the story you develop and lay out before your players can be uniquely entertaining.

Shifting to bullet points, here are three helpful things to prepare for this sort of genre adventure:

  • Clear stakes—Define in your own mind not only the identity and motives of the major NPC actors in your cosmic horror adventure narrative but also the nature of “the next big thing” that they are trying to accomplish; this is usually what the player characters will try to discover or foil.
  • A detailed timetable—Mysteries have an intrinsic timed aspect to them; they are a race against the clock before some undesirable consequence occurs. Have a well-developed temporal framework that describes in sequence the steps your antagonists are taking to advance their goal. A simple calendar or timetable of things that will happen in-game independent of your player characters’ actions unless they provide specific opposition can really help you define and present an evolving game narrative that feels real and engages your players.
  • Key locations—Have a short list of significant venues for the players to visit or interact with the NPCs in your game. Depending upon the structure of your adventure, you may organize this list into a point crawl matrix with nodes and connectors, or you may simply enumerate all of your “prepared spaces” with descriptors, key features, and clues listed in association with them. This is where you install your “timer-threat-treat” architecture. Note that not all of your significant venues are likely to be known to your player characters at the start of their adventure, but through investigation and discovery, new portions of your sandbox’s “matrix” will be unlocked, or they can be presented to the players at key points in the narrative as defined by the adventure timetable.

People who write mysteries generally start the construction of their plot in one of two places: the endgame or the inciting incident. Authors who start with the endgame envision the antagonists ultimate goal and the circumstances surrounding it, and then they work backwards to define all the prior steps that were required to achieve that goal, identifying the points where the sleuth could have obtained a clue or intervened. Authors working from the mystery’s inciting incident follow the same process of defining necessary steps toward an ultimate goal, noting branch points for contingencies where the sleuth and the antagonist cross paths (directly or indirectly) as they “discover” the eventual path of their story narratives. Either method can serve you well as a GM prepping for a mystery adventure.

The last point I will offer for your consideration involves the tone and scope of your investigative cosmic horror adventure. Experienced mystery novel fans develop considerable meta-knowledge with regard to the structure, tone, and tropes of the genre fiction they enjoy. They know to glean subtle insights from the scene of the crime of the first corpse, they anticipate the sleuth’s call to action, and they expect a midpoint setback. As the GM running a cosmic horror investigation for your players, get them prepared for the atypical set of experiences this RPG genre offers. This is not a dungeon crawl—and even when it is, it does not go down the way it does in classic fantasy settings. Make sure they are apprised of and willingly invested in the nature and tone of the kind of game you are running, so that they can play along in informed fashion with expectations well met; this can be telegraphed early in-game or stated explicitly. Most of the time, when players stumble into overt combat in a cosmic horror mystery investigation, mistakes have been made and things have gone horribly wrong. Demonstrate to them early on that noticing, gathering information, and acting with forethought and purpose are their most powerful weapons to combat the dangers ahead. An NPC’s lie during a social interaction can be as deadly to the party as any pit trap. Cosmic horror investigation is a different RPG landscape full of its own perils, and most of the time the odds are stacked against the PCs. Have fun inventing and setting up these new kinds of obstacles for your players.

Hope that helps… Viel Glück!


That may work for the climax scene but (imho) not for every scene during the story’s development. We’re heading for something different, compared to the series of mouse traps, which perfectly work for e.g. fantasy settings.

3 bullet points… a magic number :smiley: thanks!

Thanks for that hint. I read an article about four act structure and realized, that my first four sessions (that turned out to form some kind of an arc that is now completed) followed that structure… whohoooo!. Now I’m going from macro to micro, applying that structure for a session, too.

I’m fine with this. We already have some deeply detailed things I’m keeping track of… I like it!

Cheers - and thanks so far!


[FWIW to anyone who is interested, here is the most up-to-date version of my simple cosmic horror hack for ICRPG Master Edition, which I have been playing often in 2022. I call it the Cthulhack. Enjoy…]

The Cthulhack: Cosmic Horror for ICRPG
Genre rules for Lovecraftian mystery investigation scenarios by @chrisbynum
Version 0.9 for use with Index Card RPG Master Edition (Runehammer Games)

My ICRPG hack for cosmic horror scenarios is pretty simple, as follows:

  • All characters are human
  • All characters get eight (8) STAT points and four (4) EFFORT points, reflecting the fact that to be suitable investigators they should be a bit above average and maintaining the net +8 STAT bonus that keeps the characters comparable to those from other standard ICRPG settings , in the case of mind-bending crossovers(!)
  • Characters may not start with a bonus greater than +6 in any STAT
  • In lieu of Starting Loot or Starting Abilities, players choose for their characters six (6) Trained Skills and one (1) Expert Skill from the provided list of thirty common skills. (NB: There are no combat skills, movement skills, or social interaction skills in my skills list , and their inclusion is discouraged, so if you want your PC to be able to shoot a gun or dodge, put STAT points into DEX, and if you want your PC to be able to brawl, give character a STR bonus…)
  • Trained Skills are EASY, and Expert Skills are ALWAYS EASY (i.e., other applicable HARD modifiers are ignored)
  • After every five (5) Mastery points (gained with results of a natural 20 on D20 rolls for STAT checks), players can upgrade any one of their PC’s Trained Skills to an Expert Skill
  • Work with the GM to gain additional Trained Skills as Milestone rewards
  • Player characters start with D8+2 Sanity Points, gained and lost at the GMs discretion (or, optionally, the GM can start all players with one heart (10 points) of Sanity)
  • Whenever a character loses more than one Sanity Point in a round, a CHA roll is made, and on a failure the character suffers a bout of acute madness (BAM; roll on table)
  • A character who drops to 0 Sanity must roll HARD CHA immediately, and on a failure that character is rendered permanently insane (while on a success, the player suffers a random effect from the Bout of Madness table indefinitely at the GM’s discretion)
  • Player characters start with D8+2 Luck Points, gained and lost at the GM’s discretion
  • A player may spend a Luck Point to reroll a STAT check (i.e., anything but a nat 1) or EFFORT roll, or a player may deduct a Luck Point instead of losing a Sanity Point (obviating any CHA rolls for BAM)
  • There are NO Hero Coins…because the universe is uncaring and unknowable, and acts of heroism are utterly insignificant in the face of such chilling realities… :wink:

Table of Trained/Expert Skills for Characters
(Choose 6 Trained and 1 Expert)

  1. Accounting
  2. Anthropology
  3. Archaeology
  4. Art/Craft (Specify)
  5. Disguise
  6. Drive Automobile
  7. Education
  8. Electrical Repair
  9. First Aid
  10. Heavy Machinery Operation
  11. History
  12. Journalism
  13. Language (Native)
  14. Language (Foreign (Specify))
  15. Law
  16. Library Use
  17. Locksmithing
  18. Mechanical Repair
  19. Medicine
  20. Nature Studies
  21. Occult Studies
  22. Orienteering & Navigation
  23. Performance (Specify)
  24. Philosophy
  25. Photography
  26. Pilot Aircraft/Boat (Specify)
  27. Religion
  28. Ride Animal/Motorcycle (Specify)
  29. Science (Specify)
  30. Survival & Tracking

[Work with your GM to come up with appropriate additional skill areas if you don’t see what you want to complete your character concept.]

Bout of Acute Madness (BAM) Table (D10)

  1. Blackout—The acute shock of the sanity loss causes the character to make a CON save; on a failure, the character passes out for D4 rounds, while on a success they pass out for only one turn (their next).
  2. Catatonia—The acute shock of the sanity loss causes the character to make a CON save; on a failure, the character is aware of happenings around them but freezes up, motionless and silent for D4 rounds but able to attempt to roll a HARD CON success each round to shake off the it catatonic condition early.
  3. Amnesia—The character forgets who they are, where they are, what they are doing, and why for D4 rounds, and they no longer recognize friend from foe, as everyone becomes a stranger.
  4. Rage—The character is overcome with violent anger for D4 rounds, breaking objects and attacking the nearest target, friend or foe; the character can try to roll a HARD INT success each round to shake off their rage condition early.
  5. Fright/Flight—The acute shock of the sanity loss causes the character to panic and attempt to flee in a direction away from the inciting stimulus for the bout of acute madness, for a period of D4 rounds.
  6. Hysteria—The acute shock of the sanity loss causes the character to scream (1-2), weep (3-4), or laugh (5-6) uncontrollably (when the GM rolls a D6) for D4 rounds; if the PC makes a HARD INT roll at the start of each affected turn, they may take action and/or movement as normal, but on a failure they forfeit the turn.
  7. Phantom Impairment—The character suffers a spontaneous psychosomatic disability in reaction to the inciting stimulus; the GM rolls a D4, and the PC goes 1) blind, 2) deaf, 3) aphasic (cannot read, write, speak, or understand written/spoken language), or 4) paralytic (as Catalonia above, but with no early termination) for D4 rounds.
  8. Hallucination—The character suffers an appropriate vivid visual (sight), auditory (sound), olfactory (smell), or haptic (touch) hallucination for D4 rounds, with commensurate effects established at the GM’s discretion.
  9. Phobia—The character immediately acquires a new phobia (e.g., claustrophobia, agoraphobia, hydrophobia) of indefinite duration at the GM’s discretion, causing all rolls to become HARD in the presence of the inciting stimulus.
  10. Mania—The character immediately acquires a new mania (e.g., kleptomania, dipsomania, nymphomania) of indefinite duration at the GM’s discretion, causing all rolls to become HARD whenever the mania goes unsatisfied.