Blood Duty — J.R. Tomlin

Jessup is a scout for the Ilkasar Empire, even though it conquered his own people. His affair with Tamra of Wayfare Keep is the one thing connecting him to the Empire he hates. But Tamra's loyalty is to her oaths as a protector of the Empire.

While scouting, Jessup discovers the tables are about to be turned on Ilkasar: enemies are using a blood ritual to summon invincible demons, and now they're at the head of an invading horde marching straight for Tamra's forces. The two lead an army in a fierce battle against the demons, but their soldiers are slaughtered. In the chaos, Jessup and Tamra lose one another. Tamra and her remaining forces retreat to the walled city of Madrian where she leads a last stand they cannot win, while Jessup races for magical help. But even if he arrives in time, the Empire's salvation may lie in a sacrifice that will destroy them both.