Aeon 14: The Empire Series by M.D. Cooper

The proud empress whose empire is threatened. The spy operating in her court. Together they must forge an alliance and rekindle a love that deceit destroyed. Yesterday, Empress Diana discovered that Scipio is not the most powerful Empire in human space. Vast alliances have been created in the far reaches of space, and they are embroiled in a deadly war. The victor will claim all of humanity as their prize... moreThe proud empress whose empire is threatened. The spy operating in her court. Together they must forge an alliance and rekindle a love that deceit destroyed. Yesterday, Empress Diana discovered that Scipio is not the most powerful Empire in human space. Vast alliances have been created in the far reaches of space, and they are embroiled in a deadly war. The victor will claim all of humanity as their prize. For decades, Petra has operated as a spy in Diana's court, getting close to the empress so that she can influence her to ally with the Transcend on the day the truth is revealed. But after joining the empress in her bed, Petra found herself giving more of her heart to Diana than even she realized. Today, Scipio has allied with the Transcend and joined the war against Orion. With a sad heart, Petra thought her mission in Scipio was complete, but it turns out the real work has just begun. Many in the Scipian Empire see this as the perfect time to strike out and take down Diana. She and Petra must fend off cunning politicians, assassination attempts, and ready their military to join in the Orion War—all while figuring out how to fall back in love following Petra’s lies and secrecy. Even though the pressure fuels their passion, it's not enough to rebuild a relationship. Somehow Diana and Petra must fix what is broken between them and find the strength in one another to save both the empire—and themselves. less

With Petra and Diana's relationship on the mend, the pair travels to Spica, determined to strike at the Hegemony before Uriel sends her fleets against the Scipian Empire.

The inexorable march toward Sol has begun.