Demi-Plane of Dread
The Demi-Plane of Dread, sometimes known as Ravenloft or the Domains of Dread, was unique, similar to the plane that contained the city of Union in that many worlds and planes connected to it but it was still independent of them all. It was once technically part of the Ethereal Plane but was markedly different from the vast majority of that plane. Someone on the demi-plane would be forgiven for thinking that it was made out of some supernatural mist as the stuff bordered every domain and entering the mists could transport one to another location on the demi-plane. These mists occasionally formed on the Material Plane to bring individuals, buildings and even entire countries into the Domains of Dread.
The Demi-plane of Dread was controlled by the almost completely unknown Dark Powers, and sections of the demi-plane were ruled over by Darklords. These Powers had no goals that anyone could confirm, but seemed attracted to people and creatures that committed evil acts or suffered from some terrible loss. They regularly inflicted despair on the residents of the demi-plane by simultaneously granting them boons and inflicting curses. Each curse was tailored to the individual and inflicted the greatest amount of emotional harm or distress upon them. This often spurred those individuals to commit greater acts of evil. It was apparent that the more heinous the deed, the greater the power and the worse the curse granted/inflicted upon the individual until a new land was generated on the demi-plane and the individual was trapped forever within that land. These individuals became the Darklords, and they could never leave their domain. Others might be able to leave, but only if they had no great desire to, as the Dark Powers almost always intervened to dash the hopes of those trapped within their realm.