The Chaos Sway or Black Sway are the regions near to Chaos that are either BZPI signatories or realms with reasonably easy access to Chaos. While the crossing of the Abyss at the Fane of Zilla is the most traveled route into Chaos, there are in fact a great many ways and Ways that cross between the Black Zone and Chaos.
Black Sway realms are magically influenced by the great forces of chaos despite being on the east side of the Abyss. These worlds have a great deal of commerce among each other and with Chaos. The borders of such shadows are thin and are easy to pass between.
Many great nations and races exist in the Black Sway. Arguably the greatest of them is the Dufirosm. There are millions of Dufirosm realms spread across the Black Sway generally between Chaos and Azcala.