The land-quadrant castle — solid packed sand around a buried stairwell, sealed by a lightning-openable magical door and guarding the necropolis entrance.
Seen up close, the Sandcastle of the Mad Dune Mage is a three-story, medieval-style fortress of hard-packed sand (Carl likens it to a small medieval-themed casino) huddled against the Necropolis of Anser wall 'like a scared dog,' thin watchtowers flanking its façade. Its four rings of breached walls now stand open; a dry sand moat with no bridge fronts it. Crucially it has no interior rooms — just sand around a central buried stairwell, with the mage Ghazi himself dissolved through it.
There are two ways in: dig behind or destroy via the necropolis drainage panel (the 'easy' flood that liquefies the whole castle), or electrify the magical door using the two flanking lightning-rod towers during the sandstorm, which opens a glass hallway for only a couple of hours (and briefly, admitting just a few). Carl rigs a redundant cable to the drainage-wheel ring, and a lightning strike cracks the door open. The castle guards the entrance to the great tomb beyond.
A three-story sand fortress with thin flanking watchtowers, four rings of breached sand walls, a dry sand moat, and a magical front door; it appears literally built of sand, huddled against a towering carved cliff.
The land-quadrant castle — a sand shell around a buried stairwell, gateway to the necropolis and the mage's lair.