Once, a mysterious mortal race of great knowledge and enlightenment made its home in the dominion of Shom. Pilgrims journeyed to this plane in search of truth and insight, and to learn from the elders of Shom. But the ancient race vanished long ago, leaving behind its deserted temples, buried mausoleums, and monuments of stone. Now, Shom is a magnificent wasteland: a desert of white sand where titanic statues and empty cities silently guard their ancient riddles.
Shom is a large dominion. Mesas of faded orange rock and lush palm oases break up its rolling white dunes. The sky is a strikingly dark blue. A sun and moon orbit the plane, bringing day and night in the normal measure, but this sun and moon are fantastically decorated vessels of gold and silver that sail scores of miles above the ground. Although Shom is arid and swept by strong winds that drive plumes of dust from the dune crests, the temperature remains cool and comfortable.
Astral travelers nearing Shom find a brilliant blue aurora blocking their path. Those who venture through this color veil within to the dominion find themselves transported to the dazzling sands near the half-buried ruin of a city. Astral vessels alight gently on the ground. From the inside, the planar boundary resembles a strong, stationary heat shimmer mirage. Walking into the shimmer—or, in the case of a grounded vessel, taking hold of the helm with the desire to depart—returns the traveler to the Astral Sea.
https://dnd.arkalseif.info/races/races-of-destiny--81/illumian--139/index.html