Essence and Runes by Taylor Lynn

The rules of war are few: stay alive and win.
In a world of essence and runes, anything is fair game.

After leading the charge to reclaim Promithia’s northern border, Raya Ontaria—a fearsome warrior and a powerful wielder of a magic called essence—is captured and held prisoner at the court of Corath. Rather than auction her off to the highest bidder, the malicious king seems to have other sinister plans in mind.
Just as all hope seems lost, an unforeseen rescue comes from none other than the cunning Prince of Corath himself, Orion Valor.
As Raya slowly begins to trust Orion, they join forces. In their pursuit to end the 300-year war that has terrorized both their kingdoms, an unexpected spark ignites between them, yearning to be set ablaze.
There’s just one problem: Raya is already entangled with the queen of Promithia. Spurning her powerful lover could extinguish any chance of peace talks while also risking Raya’s claim as heir to the wealthiest region in the realm.
Can Raya resist the force driving her and Orion together? Or does fate have other plans?

Mortal enemies turn into unexpected allies.
An arcane power arises.
The adventure of a lifetime begins.