Black Zone Pact Instrument
At the confusing end of Shadow one comes to the Abyss of Chaos and the path to the Courts of Chaos. From the Courts a great spider of strands leads into shadow and rules over diverse realms with hardly a solid thought in them to guide them. Yet, among these worlds there are realms that have made devil's bargains with the High Lord of Chaos, Swayvil. Swayvil is a Title the ruler of Chaos holds, despite his house and line before his leadership.
These realms have entered into servitude to Chaos by signing the Black Zone Pact Instrument. The signatories thus create the Black Zone of worlds over seen by chaos. This is similar to the Golden Circle Signatory Treaty that creates the Golden Circle around Amber.