Last Exile - Travelers from the Hourglass

After the first "Last Exile" series, Claus, Lavie, Alvis, and our other heroes board the colony ship, Exile, to return home to the planet humanity abandoned hundreds of years (ago/before). A few months have passed and the quiet, peaceful life they had hoped for is suddenly disrupted when a familiar enemy shows up. How did the enemy they left behind a world ago follow them all the way home!?