Curse of Strahd
High above the river valley juts a quiet promontory upon which looms a sepulchral mansion, its turrets capped with fairytale cones, its towers lined with sculpted battlements. A third of the structure has collapsed , as has part of the roof, but the rest appears intact. A dark, octagonal tower rises above the surrounding architecture. Out of the fog comes a distant peal of thunder, quickly accompanied by the howling of wolves in the woods below, but the house stands silent, seeming like the fossilized remains of some long-dead thing smote upon the mountainside.
Argynvostholt is the long forgotten fortress of the Knights of the Silver Order. They protected the lands from evil but met their demise at the hands of Strahd's army. They were led by the Silver Dragon Argynvost.
Argynvost was killed by Strahd, before he became a vampire, and his bones collected as a trophy.
The mansion is now haunted by the spirits of the dragon's knights. Unable to make peace with their demise, the knights are cursed to remain in Barovia as revenants. They are kept prisoners by the will of their dead general's spirit, Vladimir Horngaard, who refuses to pass on in order to ensure Strahd continues his suffering as a Vampire. So great is Vladimir's hatred toward Strahd, that he will oppose any who aim to end the vampire's existence, as this will also end his eternal suffering.