Immediately upon beholding this amulet we knew that we must possess it; that this treasure alone was our logical pelf from the centuried grave. Even had its outlines been unfamiliar we would have desired it, but as we looked more closely we saw that it was not wholly unfamiliar. Alien it indeed was to all art and literature which sane and balanced readers know, but we recognized it as the thing hinted of in the forbidden Necronomicon of the mad Arab Abdul Alhazred; the ghastly soul-symbol of the corpse-eating cult of inaccessible Leng, in Central Asia
— The Hound by Howard Phillips Lovecraft
…although high impassable mountains towered on the side where Leng was thought to lie, so that none might say whether this evil plateau with its horrible stone villages and unmentionable monastery were really there, or whether the rumour were only a fear that timid people felt in the night when those formidable barrier peaks loomed black against a rising moon
— The Dream-Quest of Unknown Kadath by Howard Phillips Lovecraft
Leng or the Plateau of Leng is a cold and arid plateau which maybe somewhere in Central Asia (probably Tibet), a polar region, or the Dreamlands. There are strong indications Leng is as much part of other worlds as it is of ours; Leng may in fact be a bridge between all these worlds.
An alternate view put forward by Andrew D. Gable on the DGML is that HPL presented several conflicting views of the Plateau: in the Dreamlands, in Antarctica, in China, etc. Due to the fact it was not a place proper, but rather a descriptive term: hence, Leng could be *anywhere*.
Likewise, describing Leng as a place, a gateway or even a state of mind are incorrect analogies. Simply put, Leng is reality. It is the reality that Lovecraft always claims is beyond human comprehension. It is a point or a place or a nexus where a true piece of the universe peeks through all of its veils, and suddenly every lie and illusion become possibilities.
The myriad explanations for Leng's location are possible because they are, in effect, all possible. They are all covers of for the universe, the mask that covers the gibbering demons the lurk beneath. None of them are true, even the things we consider reality. They are all equally false. At the point where reality is exposed, we will be willing to accept any lie to cover it up, because we can accept the lie and not the truth. It is not simply more comfortable, it is the only way that we can survive.
Inhabitants
The Men of Leng
In The Dream-Quest of Unknown Kadath, the plateau is inhabitted by The Men of Leng, a race of primitive, satyr-like beastmen who live in "lone huts of granite and bleak stone villages" The Men of Leng are uncomplaining slaves to the monstrous moon-beasts, with the leaner ones toiling as crew and oarsmen on the black galleys and "the fatter ones taken away in crates for other needs of their polypous and amorphous masters."
The High-Priest Not To Be Described, The Tcho Tcho Lama
In a remote and prehistoric monastery dwells the High-Priest Not To Be Described, which wears a yellow silken mask over its face and prays to the Other Gods and their crawling chaos Nyarlathotep. In The Dream-Quest of Unknown Kadath the text would seem to suggest the High-Priest is one of the Moon-Beasts, although there is circumstantial evidence he is a degenerate Tcho Tcho.
The Tcho Tcho
In the Call of Cthulhu the Tcho Tcho's original homeland is said to be Tibet. On the DGML those Tcho Tcho who still live upon the Plateau of Leng are quite culturally distinct, this was most clearly spelt out by Mark McFadden in the Challenge from Beyond 2003, who described the Tcho-tcho of Leng and the Monks of the Zhong Mak.
The traditional Tcho-tcho include tribal shamans who can travel to the Plains of Leng, where they can contact the Tcho-tcho of Leng. The Tcho-tcho of Leng have sent emissaries into the waking world to teach the the ancient ways. Monks of the Zhong Mak train in the traditional culture and killing ways of the Tcho-tcho. Think of Shaolin who eat their opponents.
The Monks of the Zhong Mak usually wear green scarves wrapped around the lower part of their faces. This hides the fact that they have had their noses, ears, and lips removed in addition to having their heads shaved and teeth filed to points. The Zhong Mak monks are completely dedicated to combat; the noses and lips have been removed to improve their bite attack, the ears and hair have been removed to eliminate anything an opponent could grab. They tuck their testicals into their abdomen and bind their midriff like a samurai. They wear slip-knotted thongs on their limbs (like the Moro) so that they can pull the thong tight like a tourniquet and keep fighting.
The Spiders of Leng
The sentient purple spiders of Leng occupy the vales neighbouring the plateau of Leng in the Dreamlands, they are highly venemous their huge webs may span an entire valley. They are thought to be the children and servitors of Atlach-Nacha
Locations
The City of Yian-Ho
the seer who said that he alone of living men had been to Yian-Ho, the hidden legacy of eon-old Leng, and had borne certain things away from that dreadful and forbidden city - Through the Gates of the Silver Key by H.P. Lovecraft & E. Hoffman Price
Yian-Ho "where the great river winds under the thousand bridges, where the gardens are sweet scented, and the air is filled with the music of silver bells is another place who's location is hard to accurately place it maybe located in Northern China, Tibet, the Dreamlands or in the future. Inhabited by the Kuen-Yuin evil sorcerers, prior to the twentieth century the Kuen-Yuin had absolute control over millions of people within the interior of China. The Kuen-Yuin are ruled over by Yue-Laou, the Moon Maker, Dzil-Nbu of the Kuen-Yuin.
Yue-Laou
Yue-Laou is an ancient sorcerer who formerly lived in the moon, before he came to rule the Kuen-Yuin he was said to unite all those who were predestined to be together with a magical silken cord; rulership of the evil Kuen-Yuin has changed Yue-Laou and he has perverted the good genii of China, and has created from them a creature which he calls the Xin.
it not only lives in its own body, but it has thousands of loathsome satellites, living creatures without mouths, blind, that move when the Xin moves, like a mandarin and his escort. They are part of the Xin although they are not attached. Yet if one of these satellites is injured the Xin writhes with agony. It is fearful this huge living bulk and these creatures spread out like severed fingers that wriggle around a hideous hand." - The Maker of Moons by Robert W. Chambers
When the Xin hunts a man, it is aided by the Yeth-hounds, dogs without heads. They are the spirits of murdered children, which pass through the night, making a wailing noise.
The City of Sarkomand
Sarkomand is a deserted city in the Dreamlands, situated in the valley below Leng. From Sarkomand black nitrous stairways guarded by winged diarote lions lead down from Dreamland to the lower gulfs.