The universe went cold a long time ago. Only black holes remained. Them and the humans living around them. Humanity used to dominate the galaxy. Then the heat death of the universe began and they all built 50 Proto-Planets. These massive balls of Tungsten and Steel were, in reality, just massive hollow space stations. The inner walls of these beasts were 50 km in diameter, leaving plenty room for the black holes they were built around. In this inner wall lay the Hawking Radiation Plants. These plants took the energy from the Hawking Radiation and converted it into usable electricity to power the beasts. Just past these lay the Reverse Gravity Generators. These hulking machines balanced out the extreme gravitational pull of the Black Hole down to just one Gravity. Beyond this inner shell lays everything the survivors needed. Living Space, Storage Areas, Environment Management, Working Areas, Water Recycling, Yeast Vats, Etc. Out to 180km, here lies the outer shell. This half a kilometer thick layer houses everything needed for any possible conflicts, they are human after all, with enough Nuclear weapons to leave thousands of planets uninhabitable. These Proto-Planets each house 1 Trillion people and a large chunk of the knowledge database from the Human Empire. With detailed birth control maintaining population balance.
The first part of A New Universe, hope people like it. Google AI and Reddit helped me do the research so the numbers might be off.