From Tatters of the King
Leng is a legendary plateau of cold, dry wastes. Some say it is located in the Himalayan mountains of Tibet or Nepal, while others claim it is not of this world, but can still be reached through the Himalayas.
The Plateau of Leng is said to be the home of many strange creatures, including the semi-human cannibal race known as the Tcho-Tcho and the vast and terrible shantak birds.
The investigators arrived in Leng via a magical gate from Drakmar along with a retinue of Tcho-Tcho. They trekked for many hours across the frozen plains, encountered a lone shantak (which attacked and killed a Tcho-Tcho) and then eventually discovered the Upper House.
Leng seems to bathe in a perpetual twilight with strange stars in the sky. The flow of time there is unreliable.