Unanswered Questions

Thus, historians lazily marked the history of humanity prior to the previous thousand years as the Empty Ages.

Nobody knew what happened during the Empty Ages more than a thousand years ago because there was no evidence of any kind that they could work with. Rui recalled that his father had told him that the Scrier was a historian immortal sage who sought to uncover the truth of the Empty Ages.

Just what had happened to humanity prior to the previous thousand years of recorded history?

Did the lost cities have anything to do with the Empty Ages? What was their correlation to the Empty Ages, and what could be inferred about history from them? Where did the lost cities of the Beast Domain fit in the truth of the world?