All sentient beings without exception have buddha nature—the inherent purity and perfection of the mind, untouched by changing mental states. Thus there is neither any reason for conceit in deeming oneself better than others nor any reason for self-contempt, thinking of oneself as inferior and unable to reach enlightenment. This seeing is obscured by veils which are removable and do not touch the inherent purity and perfection of the nature of the mind as such. The Mahayana Uttaratantra Shastra, one of the Five Treatises said to have been dictated to Asanga by the Bodhisattva Maitreya, presents the Buddha's definitive teachings on how we should understand this ground of enlightenment and clarifies the nature and qualities of buddhahood. Jamgön Kongtrül Lodro Thaye (1813–1899), the profoundly learned and realized master who compiled what are known as the "Five Great Treasures," wrote the outstanding commentary to the Mahayana Uttaratantra Shastra translated here. Called The Unassailable Lion's Roar, it presents Maitreya's text as a background for the Mahamudra teachings in a way that is especially clear and easy to understand. Khenpo Tsultrim Gyamtso Rinpoche provided the annotations and the explanations on which the present translation is based. A renowned scholar and highly accomplished yogi, he is a living example of the ongoing tradition of oral transmission. He first visited the West in 1977 at the request of H.H. the Sixteenth Karmapa. Rosemarie Fuchs has been a student of Khen Rinpoche since 1978, and this translation was done upon his advice.