Call of Cthulhu

Call of Cthulhu is one of the oldest titles on this list, originally designed by Sandy Petersen and published by Chaosium in 1981. Set in the cosmic horror universe of H.P. Lovecraft's writings, the game runs on the Basic Role-Playing (in following: BRP) game system, which was originally designed by Steve Perrin for RuneQuest (1978) and reworked into a standalone generic system by Greg Stafford and Lynn Willis first published in 1980. It has been used in most RPGs published by Chaosium since, including Stormbringer, Elfquest, and Call of Cthulhu, the most recent edition of which (7E) was released in 2014.

Note on translation: Unlike most games in this survey, the only version of Cthulhu 7E available to the author at the time of writing was the 2015 German translation by Pegasus Spiele, which will be referenced henceforth. This also accounts for any term inconsistencies between the original English-language rules and the text below.

Free resources: 7E Quick-Start, BRP Quick-Start.

Core Mechanic

The core mechanic of 7E (referred as a "skill roll", pp. 79-87) uses a roll-under mechanic with percentile dice (d100) to resolve character actions. The simplified procedure is as follows:

  1. The player declares their character's objective and describes how they attempt to achieve it.
  2. The GM adjudicates which primary ("characteristic") or secondary stat ("skill") applies to their attempt; both stat types effectively range from 1 to 99.
  3. The GM adjudicates whether the attempted action is "normal", "hard", or "extreme".
  4. The player rolls 1d100 and evaluates it: if it is equal to 100, the overall result is a "fumble"; if it is higher than the character's selected skill score, it is a "fail"; if it lower or equal, they have a "regular success"; if it's lower than one half of the skill score, it's a "hard success"; if it's lower than one fifth, it's an "extreme success"; and if it is exactly 1, it is a "critical success".
  5. The gradient of success is based on comparing the roll result to the difficulty from step 3: if the former equals or exceeds the latter, the character reaches their objective (Yes); otherwise, they fail (No). Furthermore, a critical success brings about unexpected benefits for the character (Yes-And), while a fumble results in additional complications (No-And).
  6. If their action failed, the player has the option to "force" it, going back to step 4 of the procedure (in-fiction, it is depicted as a follow-up action) and trying again. However, if they fail once more, the GM is entitled to impose additional complications on their character (No-And) even if the result isn't a fumble.
  7. The GM describes the outcome of the character's action.

Interpersonal Skills

One primary and four secondary stats are of particular relevance to social interactions in 7E (p. 53): the "Appearance" characteristic reflects the character's physical attractiveness (erotic capital), while "Charm", "Fast Talk", "Intimidate", and "Persuade" skills represent their proficiency in corresponding types of social influence:

  • Charm (ranging from 15 to 99, pp. 52-53): The agent attempts to influence the patient by being nice to them.
  • Fast Talk (5-99, pp. 71-72): The agent attempts to confound the patient with a stream of nonsense or to talk them into believing a lie.
  • Intimidate (15-99, pp. 54-55): The agent attempts to scare the patient into submission.
  • Persuade (10-99, p. 72): The agent attempts to gain the patient's support with rational arguments.
  • Disguise (5-99, p. 73): The agent attempts to trick the patient into believing the agent is someone else. This skill isn't explicitly listed along with the other four, but nevertheless follows the same general procedure.

While interpersonal skill rolls are resolved just like any another using the core mechanic, some additional rules are employed for determining their difficulty (p. 87), which is based on the patient's stats. Specifically, the patient uses the same skill as the agent or "Psychology" (ranging from 10 to 99, p. 67), whichever score is higher, to defend against the agent's influence: if the patient's defensive skill is 50 or higher, the difficulty of the agent's roll is set to "hard"; if it's 90 or higher, the difficulty is "extreme". The difficulty is raised further if the patient's own objectives strongly contradict the agent's, while in case of NPC patients, the GM may lower the difficulty to reward particularly persuasive performance by the player. The Psychology skill can also be used proactively as a reconnoitering action in social exchanges, and is thus roughly equivalent to D&D's Insight.

While Call of Cthulhu is primarily geared towards the "PC agent, NPC patient" configuration, it does offer a mechanical framework for PC patients (regardless whether the agent is an NPC or another PC) on p. 53. On a successful influence roll against the PC, their player retains full control over their actions, however, if they do refuse to comply, the agent player may impose a "penalty die" (p. 86) on one of their subsequent rolls, which functions similarly to a disadvantage in D&D 5E. Each player (including the GM) may hold at most one such penalty die against another at any given time, and if not used within reasonable time, it may expire at the GM's discretion.

Curiously, the most salient features of the Call of Cthulhu game system, the "Sanity" stat and the "SAN rolls" based on it, neither mechanically factor into, nor are directly affected by social interactions. It would appear that confronting cosmic horrors makes investigators in Cthulhu impervious to any detrimental effects that emotional and social manipulation can have on regular people's mental health.

Finally, several interpersonal skills found in the generic BRP system are not present in Cthulhu 7E due to the specific flavor of its setting, but are nonetheless relevant to this study:

  • Bargain (5-99): The agent attempts to make a profitable exchange of goods or services with the patient.
  • Command (5-99): The agent attempts to lead a collective action, leveraging some form of authority.
  • Etiquette (5-99): The agent attempts to integrate themselves into a group or a social situation. This skill is equivalent to GUMSHOE's various parlances, rolled into a single score for convenience.
  • Status (15-99) represents the agent's social standing and, thus, their ability to manipulate their social environment. An agent can have several Status "skill" scores, each tied to a particular social grouping whose attitude towards the agent it represents.