Buried deep beneath the center of the Labyrinth lies the fortress of the Kastar Ghaash'kala, known as the Wraith-Hold to the Carrion Tribes of the Demon Wastes. The location of the Wraith-Hold is precarious, attacks could come from any and all sides and the risk of getting pincered is always present. The fall of any of the other Ghaash'kala fortresses would leave them potentially surrounded with no way out. The Kastar have a solution for this, however, they live in Khyber.
Kastar Dar is a series of warrens and tunnels carved into the walls of the Labyrinth, which all eventually reach a central cavern beneath the Labyrinth which houses the main body of the clan. Entrances to these tunnels are scattered through the labyrinth, hidden by ancient magic and natural camouflage. This is where the fortress gets its name from, as the Ghaash'kala seem to just vanish like wraiths. Each route to the cavern is laden with traps and false trails to lead those who would mean the Kastar harm astray. These tunnels are marked with secret signals that allow the Kastar to safely navigate them, whilst providing trespassers no help at all.
The inner series of caverns beneath the labyrinth house the Kastar Ghaash'kala, including their children and drok. These caverns are lit by Argent Lanterns, ancient artifacts left by the Couatl that produce sunlight, allowing the Kastar to grow crops and rear livestock in their subterranean caverns. The vast majority of the clan lives in homes carved into the walls of these massive caverns, with the exception of the deepest cavern, which they refer to as Khyber's Core.
Khyber's Core is lined with permanent defenses, traps, and magic circles. At the center of the cavern is a gated staircase that descends into Khyber, and the Kastar maintain constant vigil over this passageway, lest some horror attack them from below. They also use this passageway to send expeditions into Khyber to raid demiplanes in search of supplies.
The Wraith-Hold is also located within a Kythri manifest zone, which further helps them stay hidden as it blocks divination and occasionally causes the tunnels to rearrange.