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Cthulhu Eternal - Classical Era SRD

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“standing with his searchlight in the Roman ruin, [he] translated aloud the most shocking ritual I have ever known ... of the diet of the antediluvian cult which the priests of Cybele found and mingled with their own.”


IMPORTANT NOTE: This PDF contains the text of a full set of rules for a (setting-independent) RPG which embraces Lovecraftian adventures in the Classical eras (e.g., Ancient Greece and Rome). In OGL terms it is a “System Reference Document” (or SRD). While the rules contained in this PDF give you everything that you’d need to run a game they are not illustrated, typeset, or furnished with detailed examples as you would expect from a core RPG rulebook. Neither do they describe a particular game world, with a set of monsters, rituals, tomes and the like (although guidelines for building and encountering such elements are fully described).

Cthulhu Eternal is a multi-era, setting agnostic ruleset which aims to support inventive game designers who have original ideas for Lovecraftian roleplaying games or scenarios. It draws upon the long line of D100 games of Cthulhu-themed investigation, offering a beautifully streamlined and elegant set of mechanics to support a diverse range of gaming styles.

Different eras of human history each have their own flavor and character – due in part to the technology available, and in part due to social conventions of the day. Recognizing this, Cthulhu Eternal exists as a family of inter-related rules engines – each based on the same mechanics but tailored to the needs of a specific era.

This version of Cthulhu Eternal is specially designed to support Lovecraftian games set in Europe, North Africa and the Levant during the Classical Era (approximately 500BCE to 500CE). Empires rise and fall, religions ascend and crumble, early democratic governments vie against each other, and centuries old tyrannies. To many in this place and time the supernatural was everywhere. Gods and goddesses occupied real places in the world, mystery cults worshipped gods and goddesses with secret rites, and rituals formed a large part of public life

It’s also a region frequently name-checked in the Cthulhu Mythos. Many of the ancient, mind-shattering horrors trace their roots to the lands the people of the Classical Era call home, even if the terrors are much, much older.

The potential for Classical Era Lovecraftian scenarios are numerous. Beyond simple monster hunts, scenarios could be built around exposing a mystery cult that worships a never-before-seen aspect of Cybele. Entire scenarios could be spun around the dramas of politics between the various political families and the gods they’d pray to in order to get ahead. Organized crime groups may find themselves in a turf battle with a new group, one that seems to use rats to spy.

The Cthulhu Eternal Classical Era SRD aims to support a broad spectrum of different types of Lovecraftian game set during this period. Whether you want a gritty and historical tone or something more sword-and-sandals inspired, these rules give you the building blocks to tailor a memorable and evocative Classical Era tale of dread. Whether it's a tense murder mystery amid the complicated political schemings of the Roman forum, or an action packed chase to stop Yog-Sothoth manifesting above the Siege of Troy, these rules have everything you need.

Other versions of Cthulhu Eternal currently available in SRD form:

Each of these rulesets can be paired with the Open Cthulhu Mythos SRD, which has compatible game stats for all Lovecraft's most famous creations.

More titles are planned as future releases.

Contained within the 100+ page PDF, you will find rules covering the following topics:

Part 1: Rules of the Game

  • 1.0          Core Game Concepts
  • 2.0          Creating Protagonists (the term given to player characters in Cthulhu Eternal)
  • 3.0          The Game (skills, tests, willpower)
  • 4.0          Combat
  • 5.0          Equipment
  • 6.0          Vehicles
  • 7.0          Sanity
  • 8.0          Downtime (developing protagonists between adventures)

Part 2: Game Moderator Resources

  • 9.0          Maddening Revelations
  • 10.0        Supernatural Effects

Part 3: Game Building Resources

  • 11.0       Designing New Archetypes
  • 12.0       Translating Creatures from D100 Games
  • 13.0       Gumshoe Creature Conversion

For convenience, this pack also includes two versions of the Cthulhu Eternal Classical Era character sheet. One is a high-resolution non-fillable PDF, suitable for printing. The other is a fillable PDF sheet which will ONLY work with the full version of Adobe Reader – save the file to a local drive and open it using the Adobe Reader App (using it in-browser or on mobile devices won’t work).

12_Eternal_Char_Sheet_Medieval_-_Front_a Character Sheet Back


We are releasing this SRD to support community creators who would like to produce their own original Lovecraftian RPG creations, but who need a free and open set of rules to serve as a foundation to their own creative endeavors. As such, there are no real limitations on what you can do with this material (other than those described in the Open Game License).

Some examples of ways this SRD could be used:

  • Do you have some old Lovecraftian scenarios sitting around gathering dust for want of a free and open game system to use in their publication? Why not convert the scenario to work with Cthulhu Eternal, release them and direct readers to download this SRD to run them? Or even talk to us about bundling the SRD with the scenario PDF itself?
  • Do you have a fantastic idea for an innovative Lovecraftian game but the thought of having to re-create all the “nuts and bolts” of a game system is a distraction from your high concept? Well, you could always recycle some or all of the mechanics in this SRD to be those “nuts and bolts.” Because the material is virtually 100% open content, you can copy/paste whatever rules you want into your original creation (as long as you release under the OGL and credit us as per the requirements of the license).

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File Last Updated:
February 25, 2024
This title was added to our catalog on February 25, 2024.