Demiplane of Dread
The Demiplane of Dread is a unique Demiplane - or, perhaps more accurately, a series of interlinked demiplanes - within the Great Wheel cosmology of Dungeons & Dragons. This is the actual "world" in which the campaign setting of Ravenloft is based, and so the name is often used when trying to describe the "Ravenloft world".
The precise origins of the Demiplane of Dread are lost to history. Its creators are enigmatic beings known only as "The Dark Powers", who maintain and defend their creation with mighty magic and jealous zeal. It's believed they have some kind of mutual non-aggression pact with the various gods of the Great Wheel, but nothing canon is every defined. It is believed to lie where the Ethereal Plane meets the Plane of Shadow, but is able to manifest portals absolutely everywhere, even in places normally restricted to planar portals, such as Athas or the Phlogiston. Such portals usually appear as banks of fog or mist, but will adapt themselves to other sight-obscuring phenomena - and are usually one-way. Getting in is easy, but getting out? That's a whole other story. The only known reliable two-way portal in and out of the Demiplane of Dread is a doorway leading into the World Serpent Inn, whose doorway on the Demiplane's side of things changes every night. If you can't find that, you won't be able to leave unless the Dark Powers will it.
The Demiplane of Dread's creators have molded the reality of this world into a new fashion, forcibly imposing the rules of Gothic Horror on the setting. There are many ways that this manifests, but some of the more overt:
- Necromancy spells are empowered and rendered more dangerous; spells like Animate Dead will call up more creatures than the caster may be able to control.
- Divination spells almost universally don't function at all. Neither do spells like Detect Evil.
- Conjuration allows entities from other planes to be summoned, but they won't be able to return home when the spell expires. Obviously, quite a few of them will be very upset with their summoner because of this.
- Curses are empowered, and even non-spellcasters can potentially lay deadly or deforming curses on people if their rage or grief is intense enough to catch the notice of the Dark Powers.
- Acts of evil can result in people slowly transforming into monsters, a process called Corruption Checks. The worst of the worst can even become Darklords in turn.
Geo-physically, the Demiplane of Dread consists of various bubbles of reality, ranging in size from a single room to full-fledged countries, all floating in a sea of ephemeral mist; each of these reality bubbles (called "Domains") is typically centered around a Darklord, a villain whose evil caught the eyes of the Dark Powers and so they responded by imprisoning them within the Demiplane. 3rd edition's unpublished splatbook "Van Richten's Guide to the Mists" introduced the concept of Oubliettes, which are basically prototype or abandoned Domains that don't contain a Darklord. Precisely why the Dark Powers collect these Darklords is unknown, and theories abound; the Demiplane of Dread has been described as a prison, a gathering place for evil, a grand study into the nature of evil, a unique kind of Hell or even a Purgatory by various fans.
Another great mystery is the nature of its native population. Some Domains were physically taken from their homeworlds, but most are described as "copies" rather than direct abductions of land. This then leaves players wondering; are the locals actually "real", or are they merely soulless simulacra - props in the grand theater of Gothic Horror tales that the Dark Powers are conducting? Nothing concrete has ever been given.