The Moolavar is Sri Neela Megha Perumal in standing posture facing east and Thaayar is Soundarya Valli. The name of the Utsavar is Sri Soundarya Rajan. This temple is famous in the four Yugas. In the Thretha Yuga, Adhishesha (Lord of the serpents) performed penance here and Lord Sri Vishnu gave darshan and also accepted him as His bed. This place also came to be known as Nagpattinam. In Thretha Yuga, Sri Bhuma Devi, and Dwapara Yuga, Sage Sri Markendeya performed penance at this place. The Nagas were the first people who worshipped in this temple, even before the Chola Kings. Thereafter the Maratha and Naicker Kings who ruled Tanjavur worshipped this Lord and developed this temple. In this temple the Lord is seen in three postures: Moolavar is in standing posture, Sri Veetu irinthaa Perumal in a sitting posture, and Sri Aranganathar in reclining posture. It is believed that Sri Nagaraja was given darshan in all three positions by the Lord. The Moolavar is adorned with a copper belt depicting the 10 Avatars of Lord Sri Vishnu (Dashavatharam). The idol of Lord Sri Narasimha made of Panchaloha is peculiar with four hands denoting four different actions. The Lord is blessing Sri Prahladha in one hand, the other protecting devotees in Abhayahastham form; while the remaining two hands are representing the killing of Hiranyakashyapu. Thiru Mangaiazhwar has sung in praise of this Lord Thirumangai Azhwar has installed a golden statue of Lord Buddha, which is currently one mile from the Temple.