The Bannerstorm is a loose xtauh tribal confederation of nomads in the northern Brightness and the Riverlands. It is one of very few large-scale xtauh polities, and one of even fewer to remain relatively intact over long periods of time. In recent cycles the Bannerstorm has become a persistent threat to the cities of the Riverlands due to its increasing penchant for obtaining tribute by raiding.

The Bannerstorm derives its name from its military tactics during mass aerial attacks. Coordination of aerial maneuvers is performed by means of flying signalers equipped with horns and with colorful, streaming banners attached to their tails; they convey orders through combinations of horn calls and flight patterns.

The Bannerstorm is a multiethnic confederation of tribes with a similar pastoralist lifestyle, originally restricted to marginal grasslands on the border between the Riverlands and the Brightness proper. Each tribe consists of clusters of nomadic xtauh families, each based in a large, roofed wagon serving as a portable home. While formal authority, such as it is, is generally held by councils of elder matriarchs, who usually hold positions of spiritual significance, fathers and teenage sons, who are most responsible for the care and direction of the herds, play an outsized role in the day-to-day running of the tribe's movements and activities.

In the aftermath of the Gate Wars and the severe contraction of the power of the Riverlands cities, the nomadic tribes increasingly encroached on more fertile, and previously well-defended, territory, setting into motion a period of prosperity and population growth. As the cities began to recover in the 60s Cloud, they came increasingly into conflict with resource-hungry tribes that had no desire to be pushed back toward the desert. Tribal alliances began to spring up to more effectively take on the populous cities and the outlying villages that had turned to them for protection, culminating in the immense meta-alliance that would become known as the Bannerstorm.