Demons of the Flame Sea by Jean Johnson

Raised to understand and control advanced magics, the Fae Rii know they must be careful with the wild, abundant energies of their new desert homeland. They must also downplay the awe they inspire in the Bronze Age humans around them. Still, they have managed to create some equilibrium between the two factions, primitive versus advanced—at least, until new outworlders arrive, tipping the scales out of balance.

Strict and power-hungry, the ruthless Efrijt take the phrase “deal with the devil” to a new level. A treaty may be possible; however, the solution proposed will in turn give birth to a new problem: A chaos that will dance its way through all three races trying to survive in the burning heat of the Flame Sea…