Stygius Sector

The Stygius Sector is the Segmentum Obscurus cube of the Stygius War, the Mordian neighbourhood Tzeentch tried to drown after the Great Rift and the Iron Hands refused to abandon.

Mordian-system, Dhobash, and Prismata share the chart. The Stygius Crusade broke, then the Iron Crusade held the Iron Guard's night-world against Night Lords and Thousand Sons pressure.

The Stygius Sector still matters as Mordian's remaining lock, not as a random Obscurus label. Unofficial maps keep the Obscurus parent and leave Mordian under mordian-system.