Demiplane of Dread

Very little is known on this mysterious demiplane, also known by the name of its seemingly most prominent realm, Ravenloft. Ruled by entities known only as the Dark Powers, this demiplane's only been noted in recorded history for the last four centuries, but in that time it's pulled a number of the most significant evils of the Material realm into its mists, along with great tracts of lands and any number of innocent mortals caught in their wake. Among those known to be held here are Strahd von Zarovich, Lord Soth, Vecna, and the lich Azalin, each supposedly given great power over their domains, but absolutely none beyond them; whether they seek to reward those infamous figures they hold captive or imprison them, none can say. All that can truly be said of the Demiplane of Dread is it's a place of great horrors, completely cut off from the multiverse, and from which only a handful have ever escaped over the course of its long history. It's said that the mists of Ravenloft can reach anywhere across the Material, and that once the Dark Powers have chosen a body for it, they don't have a chance at escape.

Reference

• A Guide to the Ethereal, pg.47