Army of Fire: The Elementals Book 1

HEAD OR HEART? After the sun dies, civilization establishes itself on Xon 9, a planet with rogue Elements that affect human physiology. The inhabitants of Xon 9 soon learn to harness the powers of the Elements. At eighteen each citizen must Pronounce their Elemental, a lifelong affiliation. Ka Waylon cannot decide which Elemental to Pronounce. All her life she's been ordinary and, unlike her friends Ahna and Li, she's never felt called to any particular Element. Worse, the only advice she receives is to choose wisely. That all changes when she meets a mysterious Metal woman. Soon Ka is on a perilous journey to other worlds in order to retrieve the Elemental Stones and claim her true identity. Along the way she makes some unlikely allies and learns that she's anything but ordinary.