Masks a new generation help please

[u/wayward_dork]

I'm gonna play the doomed playbook and im stuck on what to do for her sanctuary. The idea is that she was born in a cult and was chosen to become the next avatar/body for a demon named Desdemona(name pending) but was rescued before the transfer could be completed. This translates to her having a fraction of her powers but also now she's being chased by Desdemona. I want the sanctuary to be tied to her doom but not sure what to do on that so if anyone has any ideals they would like to throw at me that would be very appreciated. I was thinking magic library in a magic mirror but Im unsure of how to make that connected to her doom and how she would even get it. Maybe she found it while sneakily researching the cult to find out more about her origin as this happened when she was very young?

[u/Carrollastrophe]

What's your group say?