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 Celestial Nadir was home to a naturally occurring magical crystal called celestial nadir crystals, which were amethyst in color. A skilled artificer could graft celestial nadir crystals onto a mortal body, replacing limbs and organs. The recipient of such grafting gained supernatural strength, speed, endurance, durability, and healing properties, depending on the type of body part replaced.

Shaddon Datharathi discovered these crystals in the mountain called Adama's Tooth near the Menhir ring leading to the Celestial Temple. He was the first to learn how to graft the crystal to mortal flesh, and encouraged many of his family members to do the same. His family mined the crystals for their magical properties, and eventually entered the Celestial Temple where they located vast sediments of the crystal. It was there that he discovered a malevolent alien entity of darkness called Pandorym.

Shaddon learned how to place special runes on celestial nadir crystals during the process that allowed him to manipulate the recipient of the modified crystals once they were embedded in their flesh. These tainted crystals were called Datharathi crystals, and Shaddon built a large mercantile business selling these crystals to rich nobles. Pandorym could possess and control Shaddon, as well as anyone who received grafts of Datharathi crystals.