The Northern Period was their most primitive era. They ruled by force, ate people, and controlled the salt mines, leaving others too weak to fight. They controlled the copper and iron mines, too, so no one could forge weapons, and forced them to offer up their own people as sacrifices.
Then they went west and learned Black Magic. Some went south, where they took to the sea and learned deception. They robbed ships, disguised themselves, and dug up vast quantities of metal, disrupting the currency market.
By the Eastern Period, they had learned to blend in with other races, crossbreeding again and again until they had created Demon Race members indistinguishable from those of other races.
Throughout the history that followed, they founded countless nations, only for them all to fall because of their brutality.
Then came the period of a certain nation, when they underwent the Faith Change Event.
After that came a long period of development. They betrayed the Demon Race and seized its nation, while some of them infiltrated the Demon Race.
In the nation they had occupied, they did their best to revise books and erase traces of history.
Then they founded a new nation. By that point, they were succubi, ordinary demons, animal demons, and so on.
Now, Lynn had written this sequence—north, west, south, east—into the Debate of Culture and Barbarians. Fortunately, though, he had called it Human-Beast Hybridization.
He hadn't explicitly stated that the so-called Human-Beast Hybridization was actually intended to breed people identical to the target race.
For example, to breed the Abyss Race, who could blend in with the Demon Race.
From the look of things, Olesian hadn't realized that this was the history of how the Demon Race had originated and spread.
He had merely used it as an example