Siva is said to have resided here in the form of Bhayananda. According to the Kalika Purana, in the beginning of the creation Siva sprinkled ashes (bhasma) at this place and imparted knowledge to Parvati (his consort). It is said that, when Siva was in meditation on this hillock, Kamadeva interrupted his yoga and was therefore burnt to ashes by the fire of Siva’s anger and hence the hillock got the name Bhasmacala.
This mountain is also called Bhasmakuta. The Kalika Purana states that Urvasikunda is situated here and here resides the goddess Urvasi who brings Amrit (nectar) for the enjoyment of Kamakhya and hence the island got the name Urvasi Island.
The presiding deity of the temple is Umananda (Tatrasti bhagavan sambhu- ruma- nandakarah Prabhu). The name 'Umananda' comes from the two Hindi words, namely 'Uma', which was another name for Lord Shiva’s wife and 'Ananda' which means happiness. In fact, Peacock Island is one of the smallest inhabited island and possibly one of the most beautiful too. The surroundings of the temple and the divine but understated beauty of the island make it a haven for nature lovers.
It is believed that, people worship here on the Amavasya day when it falls on Monday brings the highest bliss. The Siva Chaturdasi is the most colourful festival that is held here annually. Many devotees come to the temple on this occasion for the worship of the deity.
Evidence of a stone temple belonging to the post-Gupta period can be seen on the site. The site has stone sculptures and carvings belonging to the early medieval period. Achaturbhuja stone female figure still exists here besides rock-cut figures of Ganesha and a cave.
Brick temple of Umananda was built in 1694 CE by the Bar Phukan Garhganya Handique by the order of King Gadadhar Singha (1681–1696), one of the eldest and strongest rulers of the Ahom dynasty. The temple was desecrated by the Mughal Army.
The original temple was however immensely damaged by a devastating earthquake of 1897. Later, it was reconstructed by a rich local merchant who chose to inscribe the interior part of a Siva temple with Vaishnavite slogans.