Heroes of the Mists

Publisher's blurb:

Character options and new rules for Ravenloft and the Curse of Strahd.

From the introduction:

Ravenloft is neither the name of the planet, nor the name of a land. Ravenloft is an ancient castle in the land of Barovia, a nation that lies at the heart of the continent known as “the Core”.

The world itself has no name, simply being known as "the world". To some it is called the “Land of the Mists". Travellers from distant lands sometimes label the world the “Demiplane of Dread” but locals laugh at that hyperbole. Others have called the world such things as a prison for the damned, a crucible for the virtuous, or a realm of fear. To you, it is simply “home”.