Horse Plows Canyon in Vast Field
Horse Clan, always introspective and wary of the wars that tore apart the East and West in a previously Emperorless age, began trading with the barbarians of the Western Wall. Finding that the terrain across the wall was a continuation of the fields of their own, they forged an alliance, and subsequently a kinship with the Western barbarians.
When the Empire looked ready to explode into violence, the Horse was extended an invitation to join the Empire over the Western Wall. After their dealings with Horse, they had assigned them a high cultural and spiritual status, and offered to have the whole clan join at the elevated Warrior Caste of their civilization. With such an influx of skilled horsemen, the Western Empire expressed their desire to control all of the lands west of the Wall, and potentially the known world. Horse, honored by the offer presented to them and having long been disillusioned with what remained of the Golden Empire, accepted.
However bruised and battered, the Horse still considered the fields and plains of the West to be their sacred homeland. Instead of disappearing over the wall in the night, they enlisted the help of their new allies to tear down the old wall and rebuild one twice as long, twice as wide, and twice as high, but at the eastern edge of their territory, separating themselves from the Empire forever. With the industrious workers and advanced building techniques of the neighboring empire1, the feat was completed before any clan took notice, faster even than the original wall.
1 Scorpion architects secretly share their techniques with the foreigners greatly aiding in the process.