Barovia

The valley of Barovia was the oldest and best-known of the Domains of Dread. It is where the campaign takes place. Originally a location in a forgotten world of the Prime Material plane, the entire valley was transported to the Shadowfell by mists controlled by the Dark Powers. The realm was a prison for its dark lord, the vampire Strahd von Zarovich, as well as the entire population of the valley. Almost the entire valley consisted of densely forested rough terrain, with sheer cliffs and outcroppings. Few areas were easily traversable, and it was always dangerous to stray off the road. Winters were usually long and bitter. The sky of Barovia was permanently overcast with storm clouds. Even during the brightest hours of the day, light was unnaturally muted and dimmed, and did not affect normally sensitive creatures such as vampires. Originally part of a world in the Material Plane, sometime before the 11th century DR, Barovia was conquered by then-human general Strahd.