The Mani Rimdu Festival is the most important festival of the Sherpa people that is held during the tenth lunar month of the Tibetan calendar, corresponding to October–November of the Gregorian calendar. It is also the autumnal trekking season in the region when large groups of international tourists visit the Monastery to witness the festivities that last for nine days. The religious festivities involve ceremonies and meditation (Drupchen).
The meaning attributed to "Mani Rimdu" is that 'Mani' means "part of the chant of Chenrezig" and 'Rilbu' or 'Rimdu' means small red pills that are blessed during the festival. The red pills are blessed repeatedly during the festival and then distributed to all those who attend. The festival is a tradition passed on from its mother monastery, the Rongbuk. It begins with an elaborate depiction of the mandala diagram made with colored sand.
This sand is extracted from a specified location in the hills. The mandala takes four days to draw; it is then covered, and is central to the religious festival that lasts for the next 10 days. The program includes 16 dance numbers with interludes for comical effect. Finally, after all the devotees have left, the monks perform a fire rite to dispel all harm to the world.
The sand mandala specially created for the festival is then formally removed with prayers for the benefit of all sentient beings. At the end of the festivities the resident Tengboche Rinpoche of the Monastery blesses the general public after which the 'Mask Dances' are performed by the monks.
The monks perform the masked dance, to usher some of the protective deities as a manifestation of the legendary saint Guru Rinpoche, the founder of Tibetan Buddhism; the dance numbers also display the defeat of demons and the initiation of Buddhism to Tibet. Thus, Tengboche Monastery and Mani Rimdu are major attractions for tourists in Nepal.