Celestial Nadir

The Celestial Nadir was an artificial demiplane created by the original Imaskari Empire. It was used as a safe place for magical experimentation should unforeseen consequences arise. It also served as a magical bridge for the Imaskari, since many portals were situated in the demiplane that led to various locations on the Prime Material Plane.

Access
It could only be accessed from certain locations possessing standing-stone rings, and only by using a Celestial Nadir keystone. All the keystones were lost by the 14 century DR, save for one possessed by Empress Ususi. There were said to be twenty standing-stone rings that led to the Celestial Nadir. However, the only known standing-stone ring locations, as discovered by Empress Ususi, were the menhir ring at Adama's Tooth, the Mucklestones ring in the Lethyr Forest, and an unnamed ring in Skyclave city (formerly the Palace of the Purple Emperor).

Features
The plane was an apparently endless void, with roads of unsupported stone. It had free-floating lakes and islands of stone, which held a number of crumbled ruins. Some of those ruins had illumination, which may have accounted for the stars. The tombs of many powerful emperors drifted within some of the ruins. Some other objects floating through the void included cubes made of perfect mirrors, and slabs of transparent glass with the remains of monsters embedded in them. The air inside the demiplane was sharp and cold, but not damp, with a faint hint of the smell after a thunderstorm.

The stones at Adamas' Ring led to a three-way split. One of the roads continued for a few hundred paces to a geode where Pandorym's body was held; the path around the geode was overgrown with celestial nadir crystal. Another road led to an aurora-like curtain after a few miles, behind which the Palace of the Purple Emperor was faintly visible. It served as a portal to the same. The third path seemed to lead off into the distance beyond what was visible. There were dot-like stars both above and below.

The Celestial Nadir was home to a naturally occurring sediment called celestial nadir crystals, which were amethyst in color.