Deathhouse

Death House is the name given to an old row house in the village of Barovia (area E7 on the village map). The house has been burned to the ground many times, only to rise from the ashes time and again--by its own will or that of Strahd. Locals give the building a wide berth for fear of antagonizing the evil spirits believed to haunt it.
The wealthy family that built the house practiced the dark arts. Through seduction and indoctrination, they expanded their cult to include a small yet nefarious circle of friends. When word got out, the rest of the village turned a blind eye to the house and the nightly debaucheries happening within it.
The cult tried to summon malevolent extraplanar entities with no success. The cultists also preyed on visitors, sacrificed them in bizarre rituals, and hosted morbid banquets to feast on their corpses. When nothing came of these ritualized murders, the cultists' activities became thinly disguised excuses to indulge their lurid fantasies. The ranks of the cult thinned as members began to lose interest in the debacle.
Then Strahd von Zarovich arrived.
The cultists regarded Strahd as a messiah sent to them by the Dark Powers. Drawn to Strahd like moths to a flame, they pledged their devotion for a promise of immortality, but Strahd turned them away, deeming the cult and its leaders unworthy of his attention. The cultists withdrew to Death House in despair.
The cult's habit of trapping and devouring wayward visitors proved to be its downfall. On one occasion, the cult snared a band of adventurers whom Strahd had lured to his domain to be his playthings. A black carriage arrived at Death House soon thereafter, and from out of its black heart stepped the vampire himself. The cultists tried to impress Strahd. In response, he slaughtered them for slaying his playthings. Centuries later, the cultists' spirits haunt the dungeons under the house. The building itself, it seems, is unwilling to let the cult be forgotten.