Chaosium Call of Cthulhu RPG: Cthulhu by Gaslight - Keeper's Guide

Gas Lamps, Fog, and Things That Should Not Be

The year is 1890. London breathes coal smoke and secrets. The streets of Whitechapel still carry the shadow of Jack the Ripper. Empire sprawls across the globe, confident and blind. And somewhere beneath the veneer of Victorian progress, the Mythos stirs — patient, indifferent, ancient beyond reckoning. Cthulhu by Gaslight is Call of Cthulhu's Victorian-era setting, and this Keeper's Guide is the tool that brings that world to your table in suffocating, gaslit detail. Chaosium has long understood that cosmic horror is amplified by constraint — and nothing constrains like corsets, class hierarchy, and a society that would sooner commit a person to Bedlam than acknowledge what they saw in the dark.

What the Keeper's Guide Contains

This is a Game Master's resource — a toolkit for Keepers who want to run investigations, hauntings, and brushes with the unknowable in the late nineteenth century. The book opens the Victorian world with a Gazetteer of Fear covering more than 100 locations across Britain and beyond: the fog-choked alleyways of London, the windswept moors of the North, the drawing rooms and clubs where gentlemen speak of science while refusing to consider what science cannot explain. Every location is a seed — a place where something wrong has taken root, or could.

Beyond the gazetteer, the guide provides scenario seeds for Keepers crafting their own Cthulhu by Gaslight stories — hooks rooted in the anxieties and trappings of the era. Spiritualist séances gone terribly right. University expeditions that returned with fewer members and more questions. The advice for bringing the setting to life covers tone, atmosphere, and the particular horror of being a rational Victorian confronting the irrational — a character type with no cultural framework for what they are experiencing, no language to describe it, and very few people who would believe them if they tried.

Who This Book Is For

This is a Keeper's resource — written for the person running the game, not the players at the table. It requires the Call of Cthulhu core rulebook to use and assumes familiarity with the BRP system. This is not the starting point for someone new to Call of Cthulhu — it is an expansion for Keepers who want to move their campaigns out of the 1920s default and into the fog and gaslight of the Victorian age. If you have run modern or Jazz Age scenarios and want to explore how Lovecraftian horror plays when your investigators are constrained by Victorian society, class, and credulity, this guide is exactly what you need.