In The Heart of the World
Barbarians in the world of Xin are typically found at the fringes of the empire, such as The Ku Wastes.
The steppe nomads of the Ku Wastes rely on an economy of shepherding and goat-herding and raiding other tribes (as well as the prosperous provinces of Xin). The Empire has taken to annexing northern territories and buying off certain barbarian tribes, in exchange for those tribes defending the Empire from other, less agreeable tribes.
In Xin, barbarians are, for the most part, outside the rigid caste structure. At best, they are seen as uncouth rubes, to be tolerated with the bare minimum of courtesy. They are respected for their martial ferocity, but do not command the same respect as an army officer or Teiko samurai. At worst, they are seen as beast-men, barely qualifying as human and worthy only of a painless death.
However, occasionally a particularly skilled and canny barbarian works his way up the ranks of the Xin military and reaches a position of prestige and power. Though doubly derided by the haughty nobility, such men and women are often lauded as heroes of the Empire, and are invariably quite popular with the common soldiery.