Call of Cthulhu: Cults of Cthulhu

The Faithful Are Everywhere

They meet in basements, in abandoned churches, in the back rooms of ordinary buildings. They smile at you on the street. They hold positions of trust in your community. And when the stars are right, they gather — to serve something vast and ancient and utterly indifferent to human life. Cults of Cthulhu is a landmark supplement for Call of Cthulhu that puts the human machinery of the Mythos front and centre, exploring the terrifying truth that the greatest threat to your investigators may not be the creature lurking beyond the threshold — it may be the people who invited it in.

What's Inside

This 366-page hardcover supplement gives Keepers a comprehensive toolkit for building and running Cthulhu cults as living, breathing antagonist organisations. Rather than faceless cultists who exist merely to be defeated, the book treats cults as complex institutions with histories, hierarchies, resources, motivations, and the kind of internal logic that makes them genuinely unsettling. Five fully developed cults are ready to drop into your campaign across different historical eras, each with its own identity, rituals, and schemes against a world that suspects nothing.

Three complete scenarios span from the gaslit streets of the Victorian era through to the modern day, giving Keepers material that plays across the full breadth of Call of Cthulhu's era flexibility. The centrepiece of the book is its cult creation system — a structured set of rules and a dedicated Cults Worksheet that guides Keepers through building a bespoke organisation from scratch, tracking its history, inspirations, resources, and locations. The result is an antagonist group that feels like it has existed long before the investigators arrived — and may continue to exist long after they are gone.

Who This Book Is For

Cults of Cthulhu is written for experienced Keepers who want to add human complexity and dread to their Mythos campaigns. This is not an entry point for new players — it requires the Call of Cthulhu core rulebook and assumes familiarity with running the game. It is best suited to Keepers running longer campaigns where a recurring cult can develop as a persistent threat across multiple sessions, growing in menace as investigators dig deeper. The content deals with mature themes and is recommended for adult groups. If your table is ready to explore the most frightening thing in the Mythos — the people who choose it willingly — this book belongs on your shelf.