The Story of Interregnum starts in the universe of Sins of a Solar Empire, where a last ditch attempt to escape the unknown pursuers of the Vasari leads to the Sins races stumbling into the Star Wars galaxy.
2 years after the events of Rebellion (Enhanced 4X Mod era)
The years of conflict have made the political divisions between Loyalists and Rebels permanent, as the Rebel factions have broken off to form their own sovereign states. The TEC Rebels have formed a new nation called the Human Trader State (HTS), while the Loyalist continue to operate under the Trader Emergency Coalition (TEC). Believers still loyal to the original teachings of the Unity call themselves the Orthodox Advent, while the Rebel reformists have formed a new unity and refer to themselves as the Ascended Advent. The pro-peace Vasari outcasts have organized themselves into a new Vasari Independent Republic, while the loyalists continue to obey the orders of the authoritarian Vasari Central Command.
3 years after Rebellion
The Arcova Scout Frigate Pathfinder-38 finds a new wormhole on the fringes of TEC space. On traveling through it, its navigation equipment is unable to find any recognizable astronomical objects. After making star charts for the area, including a nearby Galaxy only a few light years away, it passes back through the wormhole and sends its data back to the TEC capital, where it is archived.
5 years after Rebellion
After a long period of ceasefire, diplomats from the Vasari Independent Republic successfully negotiate the Triple Alliance between the TEC, Ascended Advent and the VIR. However, celebration is brief due to the growing threat of the Vasari's unknown assailants, which are expected to arrive in Trader space in another 5 years. The Alliance and other factions begin evacuation preparations.
6 years after Rebellion
A Vasari Republic astronomer, Dr. Sularatak, begins reviewing the unknown star charts in the TEC archive, to see if the Vasari have encountered any of the stars during their long migration. Only Pathfinder-38's discovery was not in the Vasari records. That same year, Sularatak writes an academic paper suggesting the Triple Alliance could use the wormhole as a springboard for its evacuation, as it would be much easier than traveling through interstellar space to the next galaxy. He receives a grant for further study of the wormhole, now dubbed P-38c.
7 years after Rebellion
Dr. Sularatak's study produces an unexpected finding. Not only does the wormhole lead to an entirely unknown section of space, but the wormhole itself is unstable. He calculates that it will collapse on itself sometime in the next few years, before the unknown pursuers can arrive at it. The importance of his findings are immediately realized in the VIR, and after much debate they persuade the TEC and Ascended Advent that wormhole P-38c provides the best chance of escaping the unknown assailants for good.
Despite the most secret security precautions, word about this plan eventually gets out to the other factions, and after an intense campaign to seize control of P-38c, a truce is eventually negotiated by all parties. The Triple Alliance will be the first to go through P-38c, after that the HTS, Orthodox Advent and VCC evacuation fleets will be allowed to go through unopposed. Once they've arrived in the new galaxy, fighting can resume without the specter of sudden mutual annihilation.
9 years after Rebellion
The truce allows all factions to complete their evacuation armadas on time. At the beginning of the year the Triple Alliance sends millions of ships and trillions of refugees through P-38c. A few months later the HTS, Orthodox Advent and finally the Vasari Central Command also send their forces through the wormhole, each headed for a different sector of the nearby galaxy. Only a few pirates, the populations of the most remote worlds, and some stubborn Traders who believe the whole thing to be a Vasari hoax stayed in Trader space.
A Vorastra titan commanded by a member of the Vasari Central Command was the last ship to pass through P-38c. His ancestor had order the great evacuation millennia ago. The thought that they had finally escaped the unknown terror he had fled from all those years ago was an unreal feeling for him. "Whatever we find in this mess of a galaxy we're travelling to" he thought, "it cannot compare to the great evil we have finally escaped from."
10 years after Rebellion
From the bridge of the Jikara Navigator, Dr. Sularatak watched as the other side of P-38c collapsed, shrank and finally faded out of existence, just a few weeks off from his estimated date. As a scientist, Sularatak was somewhat disappointed that they would now never be able to learn a single thing about the threat that had chased his people for so long. But there was a new war to be worried about, and a new galaxy that the astronomer needed to study. "We're done here, Captain", Sularatak mumbled as he began to leave the bridge, immersed in thought. He barely heard the Captain tell his crew "Very well. Set a course for the planet the locals call... Eriadu. The fleet is gathering there, in a battle apparently just as bad as the old days." No one on the Navigator could have imagined that it would actually be worse.