The most significance mask dance Tamzhing Phala Choepa festival, bumthang is the Phag cham (ཕག་འཆམ) or the Boar Dance, in which the dancers perform wearing masks of boar. It is said that Phag cham was composed in the 15th century. At that time, Terton Rigzin Pema Lingpa was looking for a suitable place to build a monastery. It is said that, Terton Rigdzin Pema Lingpa had a vision, where Yidam Dorji Phagmo (ཡི་དམ་རྡོ་རྗེ་ཕག་མོ) or Vajravarahi, the board headed deity performed the dance and told him that he should learn this dance and perform it during the consecration ceremony of the temple. Pema Lingpa remembered the steps of the dance even after he woke up from the visionary dream. He wrote down the steps and made his followers learn the dance. To mark this auspicious occasion, Terton Rigdzin Pema Lingpa introduced the Boar Dance as the first one in the series of mask dances performed during the consecration ceremony of the monastery.

This sacred dance later came to be known as Phagcham. The foundation of the Tamzhing lhakhang is also said to have been dug by a boar, which is why the Phala Choepa festival was named. It is said that the pig borrowed deep into the soil and unearthed for the construction of temple. The performance of the boar or pig dance continues to this day at the annual Tamzhing Phala Choepa (Tamzhing festival of the Boar or Pig) held in the 8th lunar month. It is performed to ward off evil spirits, to please higher beings and spirits, and to bring everlasting peace and happiness to the people on earth.

source: www.culture.bt/textual-cp/phala-choepa-and-boar-dance-at-tamzhing-temple/