Leng is a frigid plateau variously located in central Asia (usually in the vicinity of the Himalayas), Antarctica and the Dreamlands; possibly it is in all these places and more, being a place where realities meet. In the waking world it is home to the cannibalistic Tcho-Tchos, whilst in the Dreamlands it is inhabited by the faun-like Men of Leng who may be the dreaming forms of the Tcho-Tchos and are ruled by the alien Moon-beasts. Shantaks are said to dwell in its vicinity (at least in the world of dream).
It is the location of the Elder Pharos, which is home to the last Elder One (who may be identical to the Tcho-Tcho Lama of Leng). The Glass From Leng was either made here or brought here from the Hyades.
It may be derived from Ling, the mythical kingdom of the Mongol-Tibetan hero Gesar, and a transliteration of a Tibetan term for 'monastery' or 'lamassery'.
A central Asian location could allow for a connection to the sometimes Asian and frequently multi-reality Carcosa.