From the Chaosium website:
A Study of the Religion, People, and Mythology of Tibet
Though not directly mentioned by H.P. Lovecraft in any of his stories, there are several references throughout his works to the Himalayas. Like most young men with a sense of adventure during the late 1800’s and early 1900’s, Lovecraft would have been aware of any news stories coming out of Tibet. It was a mysterious country—until 1984 visited by fewer than 2000 Europeans and North Americans, and the majority of those were among the Younghusband expedition of 1904.
The story of Tibet is as much about the country as it is about its people. With the highest points on earth, areas are nearly impossible to reach, and malevolent gods and monsters lurk under every rock. Religion, government, and mythology in Tibet are inextricably connected.
The lack of a native written language until the seventh century means that the earliest history of the country has been handed down through oral tradition and iconic images. Even until recent times there has been very little done in Tibet to explore the archaeological record, but what has been done reveals early bronze-age and previous settlements in the northern regions. Many exciting finds await discovery.