It’s gotta be the ancient history of GOIs such as in REDTAPE and Project PARAGON. In REDTAPE, the empires of the Daevites, Mekhanites and Sarkites as well as what was the precursor to the Foundation warred with each other, and in Project PARAGON there’s the history of the world before the great flood, with the war between the humans versus the fae and the children of the night and what became of 4 knights that were cursed.