From the publisher's site:
The second release in the Wormhole series, brings two entirely different races into the conflict. The Verus Republic, a vast and sprawling nation with many different worlds, races and cultures has a long history of conflict. External foes both many and varied have assailed and been assaulted by the Republic, and internal conflicts with the Nomad Cotaries and various Pirate fleets have kept the legions hard at work.
Nothing quite compares, though, to the sudden appearance of the displaced Sathrican Empire appearing on and within their borders, making claim to larger portions of their space in a bid to reestablish themselves. Petty differences will need to be set aside, and less pressing matters put on hold, while this new and grave threat is dealt with.