One More Star
In the year 2136, C.E., humanity began its mass exodus from the Milky Way Galaxy. Three hundred arks launched over the course of six years, carrying the seeds of humanity across the cosmos. The cataclysm that predicated this flight into darkness is unknown – there are many theories, but little evidence survives from the old civilization.
The Great Arks were vast ships, each intended to be a nation unto itself – some carried hundreds of thousands of people when they launched, though populations fluctuated over the centuries-long journey to the stars. Generations lived and died aboard the Arks, never knowing anything but the metal shell that separated them from the empty void.
Then, the Arks found homes in a dozen different galaxies, our Andromeda among them.