This is a work of fiction. It is meant to entertain, not instruct. It is not intended as a work of theology and, if it were, would fail utterly, as much of it would be really bad theology. Again: it is meant to entertain, not instruct.
I have chosen to base this off of several other works of fiction, largely because mixing the ideas from Mrs. Rowling with those from these other works is amusing. At times these choices constrain other choices I as an author might have otherwise made differently. Some of the theology here-in is really bad theology not because I could not imagine better, but because I sourced it in. I cannot fix everything without destroying the crossover feel that I am aiming for. In particular, much of the information in this section comes from, or rather is based on, Many Waters, although what I came up with dovetails nicely (or at least I think it does) with a concept I get from The Screwtape Letters concerning the morphology of angelic beings.
Recall that these appendices are written from the perspective of an in-world researcher. These in-world researchers are off stage both in the that they do not appear in the story itself, but also in the sense that they are not necessarily from the present as the characters in the story would perceive time. Not all of these researchers have written in the same style, nor have all aimed at, or achieved, any uniform level of professional scholarly writing. Most of these researchers are religious figures working for various in-world Vatican departments or commissions.
Footnotes are not part of the in-world document, despite any appearance to the contrary, and despite the fact that if this were a real document, it would have been written with real footnotes.
A lot of authors will try to do almost all their world building within the narrative. I realise this is technically better, but it is also harder to do. Since I am pulling from several disparate, previously existing, universes that the reader may well already be familiar with, and because I am not an awesome writer actually capable of pulling off the vision in my head, I am going to set the stage and provide some of the world building in the form of Appendices that authors generally do not publish. These world building notes are useful to understand the story, but are hopefully not truly necessary. Most (everything in the backstory section) are written from the perspective of a researcher within the universe of the narrative. I have attempted to call out the places where that is not true.