Kyuss was described as "an evil high priest who created the first of The sons of Kyuss, via a special curse, under instruction from an evil deity". Sons of Kyuss were said to be contained in the Necropolis of Unaagh, a cursed city of Sulm inhabited by undead. This was made more conspicuous since any of the contained undead that "move or are carried even a few yards from its buildings collapse into inanimate heaps of bone." This is suggested in the work to be the possible consequence of an ancient curse. That makes the creator of the undead ancient as well, painting Kyuss as once having been a high priest in Sulm.
Near the Storm Lake of the Amedio the Sons of Kyuss manifest in the vicinity after a phenomenon called the Storm of Unknowing.
In his divine form, Kyuss appears as a towering humanoid shaped entirely of green Kyuss worms, with two blazing eyes peering from beneath the hood of his ragged cloak.
The home of the "infamous Flannish evil priest Kyuss" was claimed to have been the Wormcrawl Fissure, a mile-long ravine away from the main body of the Rift Canyon.
As a high priest, Kyuss performed vile experiments while serving at the Necropolis of Unaagh - a temple meant to celebrate the dead, but he corrupted them instead.