I don’t know if this would spoil anything but how does what is the magic system in this au?
Vary good question! Although yet there is some spoilers to the answer, I will share what information I can! Hopefully to maybe make it a bit less confusing!
Mind reading/ future vision:
-source of how one obtains this power is lost to time as it has not been recorded for centuries
-visions come and go, are also no longer recorded
-fundamental unchanged from the original book series
Witchcraft (not based in real world forms of such):
-a form of natural magic that can be learned through reading and practice
-is limited by the power of ingredients used and experience of the witch
-is not good or bad, it all depends on the user and purpose
-can be made more powerful with the help of outside magical energy
Fey and elemental/emotional magic:
-less magic and more of a form of fey
-can leach off the emotional turmoil of humans and in rare cases, other supernatural entities 
-can turn those with hardship into fey, or even control other fey if strong enough
-will have a root in a aspect of nature (stone, ice, animals, plants, air etc)
-fey can take many forms and can be indistinguishable from humans
-are different from Animus magic as they are not used in order to fill a task, they exist in reaction to emotions in their environment
-will be more abundant in areas with more magic (aka, if a witch is present or a source of powerful energy)
-is relatively unchanged from original book series
- a powerful source of magic energy
-has the ability to make other forms of magic stronger
Hope this helps! It gets into things waaaay down the line but all will be revealed eventually, I would love if you all have theories and you can bet I may have answers to them in the comics as we get more into the story!