Agartha subsector

The Agartha Sub-sector is a forgotten Caligari Sector corner in Segmentum Tempestus, a poorly documented cube of decaying hives, lethal garden worlds, and Drukhari raids the Ordos long ignored.

Phaera, Tarantir, Gwaelod, and Ormeus share the chart. Tarantir hides the Stormwatchers, a Chapter that works as the Caligari Conclave's military arm. Warp anomalies and the Rift finally made the Inquisition notice.

The Agartha Sub-sector still matters as Inquisitor-Martyr geography, not as a mythical inner-earth. Unofficial notes keep the caligari-sector parent and do not invent a Terra-underworld here.