Buddhism's interaction with Boen - a shamanistic folk religion of ghosts and demons - combined with the inhospitable high places of the Tibetan plateau has led to many fables about Buddhism's taming and domestication of Tibet. Along with Guru Rinpoche's fabulous exploits, the early introduction of Buddhism to Tibet is attended by the story of a vast, supine demoness whose body straddled all the high plateau.

It was Princess Wencheng, the Chinese wife of King Songtsen Gampo, who divined the presence of this demoness. Through Chinese geomantic calculations she established that the heart of the demoness lay beneath a lake in the centre of Lhasa, while her torso and limbs lay far away in the outer dominions of the high plateau. As in all such fables, the demoness can be seen as symbolic of the inhospitableness of Tibet and its need to be tamed before Buddhism could take root there. It was decided that the demoness would have to be pinned down .

The first task was to drain the lake in Lhasa of its water (read life-blood of the demoness) and build a central temple that would replace the heart of the demoness with a Buddhist heart. The temple built there was the Jokhang. A stake through the heart was not enough to put a demoness of this size out of action, however, and a series of lesser temples, in three concentric rings, were conceived to pin the extremities of the demoness.

There were four temples in each of these rings. The first are known as the runo temples and form a protective circle around Lhasa, pinning down the demoness' hips and shoulders. One of them is Tandruk Monastery in the Yarlung valley. The second group, known as the tandrul temples, pin the knees and elbows of the demoness. And the final group, known as yandrul temples, pin the hands and feet. These last temples are found as far away as Bhutan and Kham (Sichuan), though the location of two of them is unknown.