How can an interstellar empire exist without nuclear power and warp-drives?
In the Neo-Verse, our characters travel between worlds by ‘walking the rifts’ …the terrible cold void which some can traverse in only their skin. While others need the protection of flying machines.
As for the cities and industries? These are powered by the souls of the dead. To learn more about how the Neo’Verse is structured, read the Economy of the Empire.