Rivera, K Arsenault. Their bright ascendency #1

"Even gods can be slain"--Cover

When a dark force begins to overtake the crumbling border walls of the Hokkaran Empire, an infamous Qorin warrior and a spoiled divine warrior princess set out to save their people and fufill the prophecy made at their birth

Series information from goodreads.com

The Hokkaran empire conquered every land within their bold reach-- but failed to notice a lurking darkness festering within the people. Now, their border walls begin to crumble, and villages fall to demons swarming out of the forests. On the silver steppes, the remaining tribes of nomadic Qorin retreat and protect their own, having bartered a treaty with the empire, exchanging inheritance through the dynasties. Infamous Qorin warrior Barsalayaa Shefali and a spoiled divine warrior empress, O-Shizuka will save their world and become legends-- or die trying