Children of the Sky. Volume 1. Heart of the Phoenix

Kira Skyfall has been preparing for this moment her whole life. A brave phoenix girl with white wings, hardened by training but almost devoid of magic, she sets out for the garrison of draconites, whom she has learned to hate... since birth. Two warring clans are forced to unite against a common threat — unknown monsters emerging from the ground.
 
In the garrison, Kira encounters Sheda — a grim and taciturn draconite, whose shadow magic is dangerous... and alluring. An odd, torturous connection arises between them, which Kira tries to understand. Everything leads her to an ancient legend about the Dragon and the Phoenix, but there are those who are determined to prevent her from uncovering the truth.
 
And as evil awakens and monster attacks become more frequent, Kira realizes that the key to the mystery lies within herself.