How to play Call of Cthulhu
2–6 players · 240 min
Call of Cthulhu is a horror investigation tabletop RPG based on the fiction of H.P. Lovecraft, designed by Sandy Petersen and first published by Chaosium in 1981. One of the longest-running RPGs in print, it pioneered the "investigator" model of play — characters are ordinary people (reporters, professors, doctors, private detectives) confronting cosmic horrors far beyond their ability to fight, let alone comprehend. The game is defined by its Sanity mechanic: exposure to the mythos permanently degrades characters' mental stability, making survival and competence as valuable as courage. Call of Cthulhu sessions typically run 2–6 hours, with longer campaign modules spanning multiple sessions. It remains the gold standard for horror RPGs and one of the most influential game designs in the hobby's history.
How to play
Character creation: Investigators are built from occupation archetypes (Antiquarian, Doctor, Journalist, Private Eye, etc.) and eight core characteristics: Strength, Constitution, Size, Dexterity, Appearance, Intelligence, Power, and Education. Derived stats include Hit Points, Sanity (equal to Power, max 99), Luck, and Magic Points. Most character power lies in skills — percentile values (5–80%) in areas like Library Use, Spot Hidden, Firearms, Medicine, Cthulhu Mythos, and Persuade. The percentile system: Roll d100 (two ten-sided dice treated as tens and units). Roll at or under your skill value to succeed. Pushing the Roll: if you fail, you may re-roll by describing how your investigator doubles down on the effort — but if the Push fails, the Keeper (Game Master) narrates a worse consequence. Bonus and Penalty Dice: roll an extra "tens" die and use the best result (Bonus) or worst result (Penalty) depending on circumstances. Sanity: Sanity Points (SAN) are lost when investigators encounter mythical horrors, read forbidden tomes, or witness atrocities. Each entity and tome has a SAN loss range (e.g., "1/1d6" — lose 1 SAN on a successful Sanity check, or 1d6 on a failure). When SAN drops to 0, the investigator goes permanently insane. Each loss of 5+ SAN in a single roll triggers a Temporary Insanity episode (fear, paranoia, catatonia). The Cthulhu Mythos skill rises as investigators learn more about the cosmic horrors — and every point of Mythos knowledge reduces maximum Sanity permanently. Knowledge of the universe's true nature is itself a form of madness. Investigation structure: Most Call of Cthulhu sessions follow an investigation arc — investigators are drawn to a mystery, gather clues through research (Library Use, Spot Hidden) and social interaction (Persuade, Charm, Intimidate, Fast Talk), and ultimately confront the horror behind it. The Keeper designs a scenario with multiple clue paths so no single skill gating blocks progress. Combat: Dangerous and usually avoidable. Firearms do significant damage; physical combat is chaotic. Most mythos entities are functionally unkillable. Investigators who choose to fight cosmic horrors directly rarely survive intact — retreat, containment, or cleverness are usually the correct tools.
Strategy
Call of Cthulhu rewards investigators who treat every session as a mystery puzzle rather than an action adventure. Investigation is the core skill: Library Use, Spot Hidden, and Listen are the most universally useful skills in the game. Make at least one investigator in the group highly skilled in Library Use — it is the primary tool for researching mythos threats and finding solutions. Spot Hidden reveals clues the Keeper has placed; never skip rolling it in new locations. Sanity management: SAN is your most precious resource. Strategies for preserving it: avoid unnecessary mythos exposure (don't read every forbidden tome you find), rest between sessions where possible, pursue Psychoanalysis treatment (another investigator with Psychotherapy can restore SAN over time), and keep investigators away from Major Sanity checks (encountering Great Old Ones) as long as possible. Skill specialization: Unlike D&D where a balanced party covers combat roles, Call of Cthulhu groups are most effective when each investigator has deep specialization — a library scholar, a social manipulator, a forensic investigator, a combat specialist (for when fighting is unavoidable). Generalists spread skills thin and miss key checks. The Keeper's contract: Good Call of Cthulhu play requires the Keeper to ensure there is always at least one way to progress — clues should be reachable through multiple skills so a failed Library Use doesn't dead-end the session. Players should communicate with the Keeper when they feel stuck rather than assuming failure. Knowing when to run: The most common mistake in Call of Cthulhu is trying to fight what cannot be fought. Investigators who read the signs, gather enough information, and find the unconventional solution (seal the portal, destroy the artifact, expose the cult) survive. Investigators who shoot the Shoggoth do not.
Tips
- Library Use is the single most important skill in the game — make sure at least one investigator has it at 60%+. - Spot Hidden is your clue-finding tool; roll it in every new location. - Never read a forbidden tome unless you have a compelling reason — every Mythos point gained reduces your maximum Sanity permanently. - Running away is not failure; it is correct play when the mythos entity cannot be harmed. - Push the Roll only when failure is worse than the potential consequences of a worse failure — it's a significant risk. - Investigators survive longer when they specialize; a group with overlapping skills wastes potential. - SAN loss is a storytelling mechanic, not just a stat — lean into temporary insanity episodes as character moments. - The campaign structure of long-form Call of Cthulhu (like Masks of Nyarlathotep) is one of the greatest RPG experiences in the hobby; consider starting there after a few one-shot scenarios.
Players and time
2–6 players (1 Keeper + 1–5 investigators) in 2–6 hours per session. One-shots work well; campaign play across multiple sessions reveals the full scope of the game's horror arcs.
Starter scenarios
"The Haunting" (included in the Starter Set) is the classic introductory scenario. "Amidst the Ancient Trees" is excellent for new Keepers. The Starter Set (2018) is the best purchase for new players — it includes simplified rules, pre-generated investigators, and two complete scenarios.
Campaign play
Masks of Nyarlathotep (remastered 2018) is widely considered the greatest RPG campaign ever published — a globe-spanning investigation across five countries. It runs 20–40 sessions and is recommended only after the group has experience with the system.
Common beginner mistake
Treating Call of Cthulhu like D&D and trying to fight every threat. The game is designed so direct confrontation usually fails catastrophically — investigation and cleverness are always the intended tools.
Sources & attribution
- https://www.chaosium.com/call-of-cthulhu-rpg/
Original how-to-play summary — not a substitute for the official rulebook.