The Queen of Raiders by Sarah Kozloff
The soliders of Oromondo have invaded the Free States, leaving a wake of misery and death. Thalen, a young scholar, survives and gathers a small cadre of guerilla fighters for a one-way mission into the heart of an enemy land. Unconsciously guided by the elemental Spirits of Ennea Mon, Cerulia is drawn to the Land of the Fire Mountains to join Thelan's Raiders, where she will learn the price of war.