There is a popular tale of a monster called Kirmir. People of Jaunsar were afraid of Kirmir. To appease the monster, they made a rule - that on the 6th day of every month, they will give him a goat and a man. The monster agreed. Huna Bhatt was the priest of the village and gave six sons to the monster out of his seven sons. His wife wanted to save the seventh child from the monster, and she started worshipping Mahasu. Pleased by her devotion, the god helped her, and she decided to make a temple to worship God Mahasu (or Mahasu Devta). And this temple is now known as Mahasu Devta temple.