In one of my stories, Diane gets sold to a particularly nasty kind of vampire, namely a tzimizse. These fiends are known for their ability to alter flesh, and the philosophy that mankind should transcend the bodies they were given at birth. And they don't mind trying to convince everybody else of the truth in that philosophy. Even other vampires are not safe from them.
This one, named Morrygann, was particularly interested in Diane, since she healed everything he did to her, and couldn't die: A perfect specimen for his research into the human pain-threshold.
She escaped this one too, but only after returning some of the pain he'd given her...
If you still don't understand the meaning of the tzimizse way of thought, just think Hellraiser without the leather and chains.