[She frowns a moment, shaking her head.] It was many, many years ago that the first Emperor united the clans under one rule, but legends say that his armies fought like demons, such that no clan could stand against him. It was with this force that he brought all together, and upheld his laws until the last resistance faded.

[It's a very simplified version of very complicated events, but Lan Fan isn't much of a history buff. It's close enough for someone that probably won't ever see her world in the first place.]