Ravenloft

Ravenloft, a fictional setting from the Dungeons & Dragons role-playing game, is a demiplane consisting of a collection of "domains" brought together by mysterious powers known only as Dark Powers. The domains are separated from each other by the impenetrable Mists. Each domain is ruled by its dark lord, who has committed a crime so foul as to attract the attention of the Dark Powers and be imprisoned, seemingly forever (though some can be killed and replaced), in their domain, which they are not able to escape by any means magical or mundane. The Mists play with them by denying their most coveted dream, be it love, glory in war, or the defeat of their enemies.

Ravenloft is primarily a Gothic horror setting. Dungeon Masters (DMs) are encouraged to use scenes that build apprehension and fear, culminating in the eventual face-to-face meeting with the nameless evil. Characters have a much greater significance attached to their acts, especially if they are morally impure, as they risk coming under the influence of the Dark Powers and gradually transforming themselves into a figure of evil, in the form of failed power checks.

Ravenloft began life as a standalone adventure module for first edition Advanced Dungeons and Dragons. It was popular enough to spawn a pick-a-path book, a sequel module, and in the early 90's was launched as a full-fledged campaign setting. The campaign setting was revised three times before TSR/Wizards of the Coast cancelled the line.

Currently Ravenloft is licensed to third-party publishers, who publish material compatible with the d20 System.