K'n-yan is a vast underground nation under a "sky" of glowing blue clouds similar to the Northern Lights, occupied by a hidden race of prehistoric of humanoids who sealed themselves away from the rest of the world at some time after the sinking of Mu.
Hailing from a planet much like Earth the K'n-yanians were supposedly brought across space by Tulu, founding a mighty civilisation spanning as far as the South Pole near the Mountain of Kadath. When the continent of Mu sank they decided to hole up in their underground shelter believing survivors on the outside to be in league with space-devils. Though at one point the great expanse had once been home to several races the men of Tsath managed to conquer and subdue them going on to forcibly breed them with the creatures of Yoth. After a million or two years belief in the old legends faded and rare visitors like Zamacona y Nuñez were allowed to enter to be questioned about the world above but could never leave.
The North of K’n-yan has a dry, temperate climate and a landscape of bare hills and plains made up of grey basaltic soil. A snaking highway leading to the city of Tsath crosses a slow moving river full over an ancient black basalt bridge. By 1541 the road up until this point had lost its paving but the towns on the other side remained
- Main article: Tsath
Tsath is the last occupied city in K'n-yan and the de facto capital.
A ruined suburb of Tsath leading to Nith.
A collection of deserted machine-cities from the middle period on gorse-grown plains between Tsath and the low hills of Grh-yan.
Lying below K’n-yan are the abandoned Cyclopean ruins of red-litten Yoth, the largest of which is the once great city of Zin. All of the information about Yoth's lost civilisation comes from a handful of manuscripts and carvings discovered by K'n-yanian archaeologists in the vaults buried beneath the city.
It seems that the vanished inhabitants of Yoth had been quadrupedal reptilians with the capability to create synthetic life. They used this knowledge to make and destroy a series of creatures from efficiently designed industrial and transportational animals to fantastic living shapes built for their decadent (the latter echoing Tsath's constant search for new sensations). Because of this it is unclear whether or not they devolved into the creatures found in Yoth that were used as the genetic base of the gyaa-yothn.
- Main article: N'kai
Another level below Yoth is the black realm N'kai populated with peculiar-sensed beings which had forged great civilisations without any light at all even before the emergence of the people of Yoth. The source of the multiple black idols and images of Tsathoggua. The Yothic manuscripts were scoured by archaeologists for references to N’kai, and even singular stone troughs or burrows had excited infinite speculation. Though the manuscript described it as barren the one expedition from Tsath found that it had been repopulated by a collection of formless black blobs that worshipped onyx and basalt images of Tsathoggua. Much later a second attempt to access the depths was made but neither they nor Zamacona y Nuñez were able to find the entrance.