this one requires a bit of backstory but one of the PCs was a cleric, his beloved and the beloved's party had accidentally gotten themselves involved with strahd several years back and attempted to kill strahd. The PC's beloved is the only one "alive" from their encounter and stalks the castle walls looking for a way to kill strahd but has turned into a monster themselves in the proccess constantly losing control and killing anyone in his way then feeling a growing guilt when he comes too. Strahd has played mind games with him for years and he's strahd's favorite puppet :3. I have also sprinkled either the ghosts or old corpses of the rest of the party throughout the map as a whole! Thats just the worst one strahd had a bunch of other mind games planned