The Game

Remember the days when playing Lovecraftian tabletop roleplaying games meant portraying a wheezing, neurasthenic professor or lone bookish historian, poking their noses into ancient secrets that man was never meant to know … with a grisly fate of death and insanity being more likely than not? With Open Cthulhu you can relive those glorious, simpler days when the only pulp was the discarded bodies of Tsathoggua’s trampled victims, and where the difference between a narrow escape and a lifetime locked in Arkham Asylum is a lucky Sanity roll.

The Open Cthulhu rules provide you with everything you need to play games of Lovecraftian investigative horror. They are derived from a few different sources: some parts of the Open Cthulhu mechanics come from the Legacy RPG (published by Mongoose Publishing), while other elements come from the Delta Green RPG (published by Arc Dream). The portrayal of the Cthulhu Mythos, tomes, and the supernatural are partially original to Open Cthulhu.

The Open Cthulhu SRD is divided into two parts – one which describes the rules of Open Cthulhu (for both players and Keepers), and another which describes further resources to help run games (for the Keeper only).

Here’s a quick summary of what is in each part:

Rules Section

  • How to roll dice;
  • How to generate Investigator characters;
  • How to determine whether an Investigator’s actions succeed or fail, based on their skills and characteristics;
  • Combat; and
  • Sanity.

Keeper’s Section

  • How to customize these rules to a different setting;
  • Cthulhu Mythos Magic and Tomes;
  • Powers of the Cthulhu Mythos;
  • Creatures of the Cthulhu Mythos;
  • Other Creatures and Horrors to use in your games;
  • Characters mentioned in Lovecraft’s fiction;
  • Mythos Spells and Rituals; and
  • Mythos Artifacts.