"Rebel Fay" is book 5 in the "Noble Dead" series by Barb and J.C. Hendee. In the previous book Leesil learned that his mother is still alive, but held captive by the elves, who consider her to have betrayed them. So Leesil, Magiere, and their companions set off to attempt to free Leesil's mother.
It is a difficult journey to get through the mountains, along the way they lose their supplies and faithful steeds, but in the end they manage to make it to the elven forests, with a little help from and unseen friend. Our friends encounter many strange things in the elven lands, and Magiere notices she has a strange reaction to the trees surrounding her.
Through out the series we've learned bits and pieces about Chap, the wolven Maji'hi, but in this book we finally get to know him more fully, and he learns more about himself and what happens when the Fay sent him to take on mortal form.
To save Leesil's mother will require the assistance of elves that our travelers have encountered before, elves that they have nothing but reason to distrust. Who they can truly trust, who's aligned with who, and even which side is right, are a tangled web that is difficult to unsnarl.