Black Sun Legacy of the Predecessors

Upon the twilight of the First Age of Terra, the Age of Progression,
a series of great and cataclysmic wars would erupt between its human
inhabitance and a mysterious race of invaders from the stars. The
consequences of such devastating conflicts were far-reaching. The invaders
were eventually defeated and repelled, but in the aftermath of these End
Wars, governments would collapse, and humanity would face widespread
starvation and extinction.
Thus would begin Terra's Second Age, the Age of Desolation or, as it is
more commonly known, the Thousand Year Darkness.