Kasimir's sister, executed by her own folk for consorting with the Devil
From Kasimir’s telling of the story, Patrina was a witch living among her clan, a powerful practitioner of “the Art.” After the Curse of Strahd fell over the land, Patrina audaciously consorted with the Devil himself. As punishment and, perhaps, out of a mix of fear that the Devil had corrupted her and mercy to save her from the dark path on which she trod, Kasimir ordered the clan to seize her and stone her to death.
Enraged, the Devil ordered that the dusk elves hand over Patrina’s body, which he then entombed in the crypts beneath Castle Ravenloft. As punishment for what they had done, the Devil ordered his henchman, Rahadin, to murder the first-born children of the clan, just as Kasimir had ordered the murder of his older sister. Secondly, as Kasimir had instigated the execution, Rahadin cut off his ears and let him live with his disfigurement.
Patrina has lain in the crypts of the Devil’s castle for centuries, but according to the dreams Kasimir experiences, she has not rested, nor has her soul moved on. Tormented by the reflection of what she had done, she reached out to her brother and sent him visions of secrets hidden away in the Amber Temple that would help him against the Devil. Moreover, these visions told him that there was a way to restore Patrina to life so that she could help him.