The Fall of Humanity
Thousands of years after humanity first set foot on their home world's moon, an empire had risen. The Imperium of Humanity spanned across the galaxy. Millions of systems owed their loyalty to the Imperium. Humanity had firmly placed itself as the largest, most powerful species within the galaxy.
To be truly human was rare, especially the further from Earth you traveled, as to colonize these harsh new worlds, humanity sacrificed their own genetics. With each world conquered a new breed of Lessers was born within the laboratories of Earth, genetically modified as the perfect organism to inhabit and rule whatever world had found itself a member of the Imperium.
Throughout the centuries humanity had waged countless wars on the frontier of their growing empire. While intelligent life is rare within the galaxy, thousands of intelligent species had been discovered, many of which were spacefaring as well, with most setting up their own empires. The ruthless nature of the Imperium saw these species either join or be exterminated.
While the inner Imperium saw peace and prosperity, the further out one went from Earth the more Humanities virtues were dimmed and distorted by the vast distance and genetic modifications that were placed upon the ruling Lessers.
As humanity thinned itself, both in an expansion and genetic sense, war and corruption began to infest. Then all communication from the inner Imperium vanished in a single moment. The inner systems sudden disappearance became known as the Great Collapse. Within that moment, what little light the outer Imperium saw from Earth was extinguished and the infestation became all consuming.
Humanity had fallen, and the outer Imperium collapsed with it in an instant. War broke out among the remaining systems of the Imperium. A power vacuum had been created as each system fought to either conquer and reinstate their version of the Imperium, or dug in and defended what little they truly had.
With the fall of Earth and the inner Imperium, a darkness is spreading throughout the galaxy. A new threat to all intelligent life has risen. While what little of humanity is left squabbles amongst themselves, it grows ever closer. Humanity has already fallen.