Until the Sky Falls

After the previous Death Empress dies in a tragic accident, young Nimue is snatched from her small fire worshipping tribe to train for a chance to become her replacement. With no home to return to, she can only hope to survive as long as possible when the infighting begins. The boat is rocked when she forms an unlikely alliance with Raliene, another of the ten possible future emperors, whose religious fervor drives her every decision. Neither one could win without the other, but neither can succeed while the other remains.

Are they each other's biggest enemies, greatest allies, or is the paranoia self-sabotaging?

The picture in the cover is Le Chevalier aux Fleurs by Georges Rochegrosse.