Killing Immortals and Demonic Traces

One is a heroine who commands thousands of troops, and the other is a thin deserter of unknown origin. They are old enemies, and they also rely on each other. A battle to destroy the country pushes them into the gears of fate. He transforms into a demon, and she controls the gods of the righteous way. A war between immortals and demons that shakes the six realms is about to begin! Is it a demon or a fairy, is it good or evil, is it obsession or is it life and death?