Mystical revelations as a source of spiritual instruction are present in almost all world religions. In Tibetan Buddhist tradition, such revelations, called terma, hold a special place, keeping the teachings of the Buddhist Tantra alive and relevant for many centuries. In his truly unique study of this tradition, the author, with encyclopedic thoroughness and relying on deep knowledge of the issue, introduces the modern reader to such an important layer of Tibetan spiritual culture.