Peering into the Abyss: The Cthulhu Mythos Skill

Of all the skills on an investigator’s character sheet, the most alluring, but least used is Cthulhu Mythos. This suits the Lovecraftian perspective that humans stumble around ignorantly in a massive and incomprehensibly dark universe. The limited access to eldritch insight serves both Keeper and players well when aiming to capture this particular tone; however, it potentially restricts players aiming to recreate investigators in the image of Dr. Henry Armitage or Keepers intending to run a double-barrel Pulp Cthulhu campaign. We intend to review the use of the Cthulhu Mythos skill in the Classic and Pulp settings and introduce a Pulp-oriented Cthulhu Mythos skill expansion. The discussion seeks to inspire both Keepers and players to mold the Cthulhu Mythos skill to best suit the entire table’s style of play. 

In Call of Cthulhu, nearly all investigators begin the game with no points in the Cthulhu Mythos skill. An optional Mythos Experience Package in the Investigator Handbook (page 62) suggests increasing the level to 1D10+5 percent while incurring appropriate SAN deductions. Using the skill allows Investigators to recognize monsters, tomes, artifacts, and Mythos deities. This differs from the Occult skill, which focuses on more mundane secrets passed down through human civilization over the millennia rather than the impenetrable, aeons-old cosmic horrors contained in the Cthulhu Mythos. In both Classic and Pulp, Investigators raise their Cthulhu Mythos value through Mythos encounters and tome study. As the skill level increases, the investigator’s maximum Sanity undergoes a corresponding reduction. If a nonbeliever, the study of tomes permits an investigator’s skill improvement without SAN loss; however, once they witness the Mythos they lose SAN equal to the accrued skill points. In addition to this loss from tomes, the first Mythos encounter grants a five percent increase to Cthulhu Mythos with one additional percent for each subsequent event. This leads to a very slow incremental increase from potentially mind-blasting sanity loss. In Classic, the most effective means of improving the skill is through tome study, but this process takes a substantial time investment by the investigators. 

Once they have gleaned the terrible secrets of the universe, many investigators hope to put their hard-earned skills to work. In most cases, though, they must make heroically challenging rolls for cryptic information, and, even if successful, they receive no opportunity to increase their skill during the Investigator Development Phase. The restricted progression and scant efficacy of the Cthulhu Mythos skill serve one-shots and short campaigns very well. On the other hand, epics, which feature many and varied Mythos encounters (like MoN), afford great opportunities for investigators to reasonably build upon the skill. Further, due to the wide scope of these adventures, the risk of ruining the investigative mysteries through successful Cthulhu Mythos skill use is very low. For Keepers worried about unscripted revelations following an investigator’s success, consider delaying the clue by providing it in a dream, sudden vision, or delusion sometime later. If you know your players like to roll against Cthulhu Mythos, consider preparing a few snippets of tantalizing information that deepen the scenario’s flavor or offer a small advantage against the final encounter. Be strong, an Extreme success does not earn anyone permission to review the monster’s stat block or rifle through your notes. 

As with Classic Call of Cthulhu, the Pulp rules adhere to the Lovecraftian principle that magic lies beyond the reach of the average, sane person. But no Pulp hero is average. The published rules allow for quicker tome study and also offer an optional development phase for improving the Cthulhu Mythos skill allowing for increases of 1D4 points (page 72). Additionally, heroes may employ their Mythos knowledge (page 37) to achieve certain effects, which include the following:

• Inflict physical harm (Cthulhu Mythos vs. opposing POW)
• Banish a monster (spend MP equal to ⅕ POW, Cthulhu Mythos vs opposing POW)
• Commune with recently deceased
• Commune with long-dead being
• Invoke a physical ward
• Comprehend Mythos language – 8MP plus 1D6 SAN

To build upon and slightly modify these rules, we suggest allowing each hero to select a Mythos specialization either before or during their adventures. Each specialty affords access to a narrow set of skills, including the aforementioned effects provided in the rules. This allows the inquisitive to delve into darker mysteries and provide unique abilities to investigative team members. A heroic investigator need not be a believer (Keeper Rulebook, page 179) to select their preferred specialization, but they must become one to use it. Our suggested specializations and sample uses include:

Alien Technology: interpret alien symbols (Regular), identify alien technology and its use (Regular), gain a bonus die when using alien technology (Hard), improve upon alien technology (Extreme)

Example: While exploring a moon base, an investigator recovers a mist projector from a felled mi-go. Not only do they understand its function, but, with an Extreme success, they modify the apparatus to affect their alien foes. 

Arcane Artifacts: discern the use of an artifact (Regular), identify its particular risks (Hard), craft an imitation (Hard), recreate or repair the artifact (Extreme, at Keeper discretion) 

Example: After cracking the safe of a vacationing megalomaniacal industrialist, a Regular success identifies a crystalline power source hidden amidst a trove of treasure. Before pursuing the second lost crystal in the Amazon, the investigator attempts to recreate it, but fumbles their roll and complicates their mission by drawing the attention of a ravenous extra-dimensional demon.

Dark Deities: recognize a Mythos deity and/or its worshippers (Regular), harness the power of a Mythos deity to inflict harm (Pulp rules), impersonate a high-ranking cultist (Hard), summon or communicate with Mythos god (Extreme)

Example: While traveling through the Himalayans, the investigator spots a band of travelers wearing colorful robes. With a Hard Cthulhu Mythos success, an investigator identifies them as worshippers of Cthugha and feels confident she can approach them and display the appropriate signs of reverence to their god. 

Mythos Monsters: identify the entity via physical evidence or description (Regular), discern the creature’s motivation when possible (Regular), determine a weakness (Hard), summon or banish (Extreme or use Pulp Rules)

Example: Stumbling upon a crime scene, an investigator recognizes the mad gibbering of the fleeing ghoul, who committed the savage murder. After confronting the ghoul in his lair, the investigator banishes the unrepentant graverobber to the Dreamlands. Despite this success, the creature still haunts the investigator nightly…

Necromancy: extract essential salts (Regular), commune with the recently deceased (Regular), speak with the long-dead (Hard) and short-term corpse animation (Hard), resurrect the dead (Extreme)

Example: As a torpedoed ocean liner rapidly sinks, an investigator extracts the essential salts from a fallen cultist (or dear ally) with a Regular success. They make later use the vital substances to briefly animate a cadaver (Hard) and attempt an interrogation. 

Spells and Magic: learn an additional spell during tome study (Regular), identify a spell or ritual as it is being performed (Regular), invoke a ward (Hard), identify the residua of a spell or ritual (Hard), counter or learn the spell (Extreme)

Example: During a combat encounter, a demented wizard scrawls symbols on the floor as his henchmen attack the investigators. An investigator makes a Cthulhu Mythos roll to determine what the madman aims to achieve. With an Extreme success, the investigator identifies the incantation as a gate spell allowing them to hastily alter the portal and remove several of their adversaries from the fray. 

With Mythos Specialization, the investigators gain an amount of Cthulhu Mythos skill points equal to Sanity Loss + 5 for their first true encounter with their specialization. After this, they gain Cthulhu Mythos points equal to the amount of Sanity Loss related to their particular specialization, instead of just 1 point. Consequently, the acquisition of skill points relies on Sanity loss and drives interesting player choices. Some players may actively seek out dangerous secrets and encounters to further their knowledge, while others entirely decline to employ the skill in hopes of preserving their tenuous grip on reality. 

When employing Mythos Specialization, you can bypass the optional Pulp Cthulhu Mythos Development Phase and allow players to raise their specialization by the standard Development Phase process (rolling to fail, adding 1D10 points) or require the focused study of appropriate tomes. By permitting focused tome study, Keepers can reduce study time and apportion percentages based on the tome’s specific contents. This allows investigators to pass a tome around while each gaining a different benefit from it. For spellcasters, a Keeper may reduce Cthulhu Mythos points earned in exchange for learning new spells. 

For Mythos Hardened investigators (Keeper Rulebook, page 169), once their Cthulhu Mythos score exceeds their Sanity, they begin to take half Sanity loss for exposure. Keepers can decide whether to exclude this rule from their game or apply it specifically to Sanity loss related to Mythos Specialization. 

Bear in mind, the above examples simply serve as suggestions and inspiration if you feel compelled to tinker with the Cthulhu Mythos skill. For players, consider presenting this to your Keeper if you feel like this would enhance your enjoyment of the game. We have enjoyed introducing this concept early in the campaign and allowing our players to drive their character development and interests through their specialization. In many situations, it allows an emergent style of play, as we let players rely on their imaginations and personal Mythos knowledge to fill in the details and drive the investigation. By broadening the application of the Cthulhu Mythos skill, it brings a collaborative and often surprising atmosphere to the table. 

Disclaimer: No scenario should ever hinge on a single skill roll. The purpose of rolling dice is not to allow or prevent the investigators from doing something, but to enrich the roleplaying experience. If you believe modifying the Cthulhu Mythos rules breaks your Call of Cthulhu game, by all means, ignore all of this nonsense.