Strahd

Count Strahd von Zarovich is the dread vampire lord of the land of Barovia, overseeing his cursed domain from the heights of Castle Ravenloft. His land is cursed such that outsiders can enter, but no one can leave because of the murder fog that surrounds the land, and he sees that the citizens of his land are kept on an uneasy line between comfort and misery.

Sergei von Zerovich
Strahd once had a brother, Sergei von Zarovich who was a brave and noble man - the mirror opposite of Strahd.

Debt to the Vistani
During one of Strahd's military campaigns, years before he became a vampire, a group of Vistani rescued him after he was wounded in battle. These Vistani not only nursed Strahd back to helath, but also delivered him safely home. As a reward for their generosity, Strahd declared that all Vistani had the right to come and go from his land as they please, and this privilege extends to the the present day. Thus, Vistani can travel freely through the fog that surrounds Barovia, without fear of harm or entrapment.

Strahd's spies
Strahd's spies come in many forms, including bats and wolves under his control in addition to various humanoid henchmen.

Tarroka Fortune Reading
Madam Eva's Tarroka card reading has revealed clues to the locations of 3 ancient treasures that can be used to oppose Strahd, as well as who his nemesis is, and where the heroes can ultimately face him in Castle Ravenloft.

See Tarroka Card reading.