The First Imperium — Jay Allan

Book 4 of the bestselling Crimson Worlds series... The Alliance and its colonies have called a truce and signed the Confederation Agreement, providing the frontier worlds with guarantees of self-government. No one expects the deal to last, and both sides are preparing for the next showdown. But from the depths of space another challenge is coming, one that will endanger the very survival of mankind and force not just the Alliance and its colonies, but all of the Superpowers, to join forces or face annihilation. The dusty ruins the Alliance discovered on Epsilon Eridani IV were built by an ancient race, eons dead. But their guardians remain, and the disturbance of the long silent cave triggered an automated alert, one which has been heard. Erik Cain and his Marines grimly take to the field once again, for what may be their final battle, against the robotic legions of the First Imperium. But facing a ruthless and technologically superior enemy may be easier than learning to fight alongside old enemies.