First I'd tie her down with her arse hanging over the edge of a bench and cut her legs off, making sure her legs are properly dislocated out of her pelvis. I've always wanted to fuck a legless woman so I can get my cock as deeply inside her as I possibly can.
After that, I will force open her cervix one finger at a time until I can fit a fist through with ease. Once removed, I'd install the crystal in myself and finish her off by forcing both hands into her womb and tearing her open as far as I could. First with my hands, then by reaching inside her with a blade and stabbing outward see she sees it protruding from her uterus. I'll then see how long she last as I fuck her a new cunt in her abdomen.
If she lives long enough, I'll pull the knife back inside her then push towards her head until my arm is completely inside her to the shoulder.
If I'm honest, I'd probably fuck her thrashed cunt again, and then fuck her new gut cunt and cum directly into her womb.
There would probably be some ovary-eating involved too.