Lineage of Rechungpa.
Buddha Amitayus -> Indian Mahasiddhas -> -> -> Lama Walachandra -> Rechungpa brought to Tibet -> after number of Lineage Holders -> -> -> Drukpa Choegon & Drukpa Yongzin Rinpoches of Dechen Choekhor about 500 years ago.
Amitayus - The Buddha of Long Life, Merit and Wisdom. He is the sambhogakaya aspect of Amitabha Buddha - the Buddha of Limitless Light and Life; and is the principal Buddha for overcoming the power that death and ignorance have over us. With these removed, we can fulfill our true human potential - the achievement of ultimate happiness through realising our primordially enlightened nature. Buddha Amitayus is one of the Four Main Essential Practices of Drukpa Kargyu.
Amitayus is depicted as holding a vase of amrita, the precious nectar of immortality which confers longevity, and the leaves of the ashoka tree, which symbolize long life without misery (shoka) of disease. His body is said to be akin to a ruby mountain, radiant like a brilliant pure jewel, eliminating the ignorant and suffering of beings.
Objective & Benefits of the Practice:
Buddha Sakyamuni has spoken about the power and the great benefit of Buddha Amitayus's mantra. According to the Sutra, it's said that the merits accumulated from offering Buddha with the most precious stones that fill the universe can be counted, but the merits of recitation the mantra of Amitayus is far too vast to be measured. Lord Buddha also given the example that reciting Amitayus mantra is liken a ninety nine millions Buddhas remain in Samadhi and chanted the mantra in one voice … thus it's extremely powerful.
Amitayus is the Buddha of boundless life, merit and wisdom. By engaging in Amitayus practice we can develop these qualities, which are essential for our spiritual development, and eventually attain the deathless state of enlightenment.
Sincere practice and devotion to Amitayus is said to help eliminate all obstacles to long life such as sickness and pain, and pacify the possibility of untimely or premature death. The Amitayus practice is important because longevity is an essential contributing condition that allows us more time and opportunity to practice the genuine Dharma to liberate oneself from the Samsara of cyclic existences. We can also engage in this practice to remove obstacles that endanger the lives of others.