Vengeance: Book 3 of The Shadow War Chronicles

The Crew of the Revenant must save Earth from the coming threat, a new leader has emerged in the aftermath of Jamestown, Vengeance has set his sights on humanity, and nothing will stop him from Subjugating the planet.
The Empire is forming an army to take over the galaxy,
Seafu must race to build a coalition to stop them.
There will be new enemies and unlikely allies and
Earth will finally discover it is not alone in the universe.