Buddhism came to Tibet in the imperial period, under kings who saw in it both truth and statecraft: Songtsen Gampo took Buddhist queens from Nepal and China in the seventh century, and Trisong Detsen invited the Indian master Shantarakshita and the tantric adept Padmasambhava to found the first monastery at Samye around 779. Tradition holds that Padmasambhava bound the local gods and demons of the plateau to protect the new teaching, a story that captures the actual settlement: the mountain gods, spirits of place and household rites of older Tibetan religion were not abolished but enlisted.
Bon, Tibet's other organized religion, understands itself as the older faith, brought from the western land of Zhangzhung; in its surviving form, documented in Per Kvaerne's study of its iconography, it closely parallels Buddhist monasticism, scripture and art while keeping its own founders and lineages. Scholars debate how much of it preserves pre-Buddhist religion and how much grew alongside its rival.
Tibetan Buddhism proper organized into four great schools, Nyingma, Kagyu, Sakya and Gelug, transmitting tantric practice through empowerment and oral instruction from master to disciple. Its distinctive institutions include the tulku system of recognized rebirths, of which the Dalai Lama, held to embody the compassion of Avalokiteshvara, is the most famous; the beloved poet-saint Milarepa, whose songs carry Kagyu teaching; devotion to the savior goddess Tara; and the funerary literature of the bardo, the between-state, known in the West as the Tibetan Book of the Dead.