1. I would like for them to be a second set of antagonists, since the Ragged (Raggard?) Brotherhood hasn’t done anything in a while. And I very much enjoy multiple antagonists in a story, especially when they don’t necessarily get along.

2. Yes.

3A: (Blood magic) Basically using blood as a medium for magical energy, instead of it being incorporeal. For example, the character I have in mind, doesn’t ‘regenerate’ her magic over time, she needs to either drain blood of a creature to regain it, or do a special ritual that requires her own blood. Change shape of her own blood yes, and to an extent others. It also allows for a lot of out-of combat uses, such as tying two individuals together with their blood. (Not literally connecting them, but you get the idea.) As well as various other miscellaneous things.

3B: Limited shape shifting as in a new form would require years of practice to create and master, so the user only has limited forms to choose from, and it requires the physical mass and magic to use.