From the announcement:
It is a dark time for the galaxy. The Old Republic is dead. In its place, the Galactic Empire has seized control of the galaxy, subjugating worlds with unprecedented speed and ruthlessness. Every day, the Imperial flag spreads to new worlds. And worst of all, there are rumors that the Emperor has been developing a new superweapon, one with the power to destroy whole planets.
What do these rumors mean? Is this the death of freedom? Or is it the first spark of a war that will shake the galaxy? The time has come for you to decide.
The Rise of the Empire expansion for Star Wars™: Rebellion is now available!