As you may have noticed, if you've looked at my map of the Forbidden Lands (which is not meant to be comprehensive; many locations exist which aren't labeled on that map), one of the notable locations is the Plateau of Leng. Ringed by titanic mountains of madness (heh), but with Lake Hali and the Tarqan Lake on its southern and southeastern edges, the plateau is difficult to reach, nearly impossible to climb, and extremely uninviting, just from an environmental perspective. Very little grows on its cold, windswept surface, which is extremely arid and littered with ancient menhirs, standing stones, and crumbling ruins of ancient walls and structures who's purpose can only be guessed at today. The few creatures that eke out a living on the Plateau of Leng are carnivorous giant spiders and cannibalistic, pale people, similar to the inhabitants of the Cannibal Isle, and probably ethnically related to them. These "Men of Leng" as they are known, have a tendency to devolve into beast-like sub-humans over time, although their curse appears to be different than that of the Islanders.
Despite this, there appear to be other inhabitants of some kind as well. Eerie howls of unknown provenance echo across the vast table-land, and the scratching and digging of some kind of creature that is rarely glimpsed but frequently heard can be picked out by keen listeners as well. These glimpses seem to be of pale, lumpish creatures that are not even vaguely humanoid, being instead hunched, toad-like creatures, like Deep Ones who have lived for generations in caves and become pale and eyeless.
This bleakness is broken by a few landmarks:
Carcosa. Located on the edge of the plateau, with sheer cliffs that fall into the dark, silent waters of Lake Hali from which nearly constant mist rises, this abandoned and cursed city has no inhabitants that can be seen, but there is always an eerie feel of watchfulness and menace. A strange flapping sound, as of rags hung out in a strong wind, echoes through the deserted stone. According to patchy myths and legends, the King in Yellow himself might haunt Carcosa at times.
Sarkomand. A city of the Men of Leng, where they have some measure of culture. Ruled over by the Elder Heirophant (also known as the Tcho Tcho Lama, or the High Priest Not to Be Described), a mysterious figure who also hides himself behind yellow robes, this is a sinister city where peoples of the Lands of Three Empires might come as slaves--possibly--but they don't live long. Rumors are that vast caverns called the Vaults of Zin lurk underneath the city.
Iganok. A small port town on the shores of Tarqan Lake. The peoples who live here are subject to the Hierophant of Sarkomand. In addition to the sinister traffic in slaves for unknown purposes, they also mine onyx from the slopes of the plateau itself.
N'gah. Actually, a city in the Hsan Jungle just to the west of the plateau, the carnivorous and intelligent (yet barbaric) apes and monkeys that live here also have a subject relationship of sorts with the Heirophant, and provide many of the goods that the Heirophants people need to live--although they also have a fractious relationship, since the apes cannot live with anyone, and frequently bring violence to the people of Sarkomand, Iganok, and anyone else that they can reach.
Kadath. A city atop the mountains that overlooks the plateau with a commanding view, this cold, black-stoned fortress-city is the home of the Great Ones--mysterious beings who nominally (but passively) rule the entire plateau.