"Drub" means Accomplishment and "chen" means Great, "Drubchen" means Great Accomplishment practice. It is a traditional form of meditation retreat in Tibetan Buddhism that lasts for about 7 or 10 days.

It involves a large number of monastic and lay practitioners and is led by at least one high lama. The Drubchen is regarded as a very powerful practice, and is said to act as a remedy to the negative forces at work in the world, and to promote inner peace, peace within the community and world peace. Full attendance at a Drubchen is said to produce the same benefit as practicing alone in solitary retreat for 7 years. The practice requires prayers and mantra to be recited by practitioners, taking turns, for 24 hours a day throughout the period of the Drubchen.

The Sampa Lhuendrup Thongdroel was commissioned by the ninth Gangteng Tulku Rinpoche for Gangtey Gompa. The Thongdroel, 45 feet high and 59 feet wide, depicts the 13 images of Sampa Lhuendrup with Padmasambhava in the center surrouded by the eight manifestations of Guru Rinpoche in an inner ring.

The Thongdroel is studded with precious stones, including turqoise, dzi, and pearl, contributed by students of Gangteng Tulku Rinpoche. Gangteng Tulku Rinpoche funded the Thongdroel at a cost of $51,000 US, excluding the precious stones and other trappings. It took artist more than 16 months to create the Thongdroel. The Thongdroel has been consecrated by all three emanations of Pema Lingpa: Thukse Rinpoche, Sungtrul Rinpoche and Gangteng Tulku Rinpoche.