I am looking for a series. It may be 5 books, but I am not totally sure on that. I read the book roughly 15 years ago and believe it was somewhat new at that time.
The story itself is wrapped around a parent story, which treats it as a history book on how magic got lost in the world. The parent story mentions that reading this true history is forbidden and is made up as some advice for scholars reading it.
The main story is about a world where magic is vanishing. Many people in this world believe that magic can only be used by men. Typically they charge their magic through the stars. That belief is false, however.
The protagonist is a little girl in the beginning who lives on an apple plantation. She has to leave however as the plantation burns down. We later learn that she charges her magic through the sun (moon?), which makes her quite a lot more powerful.
I remember that the antagonists of the story started out as somewhat normal mages who used a spell gone wrong that they wanted to use to get rid of all the bad inside them, but got rid of the good instead. One of those mages was a bit more complex as he saw good and bad in everything and as such the spell failed to get rid of the "gray" areas in him, meaning he retained some good.
Over the course of the story the girl meets a man who does not age and is an adept swordfighter. (I believe he only has one arm tough, not completely sure.)