The sanctum of Thiruvedanthai has a huge Varahamurthy (Boar deity) with Bhudevi (Goddess Earth) at its left. The Varaha is an Avatar of Lord Vishnu. Here the Varaha relic is more than seven feet tall and its right foot is raised knee-high, resting on the many-hooded serpent Adi-Sesha, serving as his couch, throne, umbrella and footrest. The temple was built in seventh century AD and the sculpture belongs to seventeenth century AD of Vijaynagara period.
The temple derives its name as the 9 feet high Lord Vvishnu's idol has his consort Bhudevi seated on his left thigh. The word 'Thiru' means sacred, 'Ida' means consort and 'Venthai' depicts left side.
The sculpture of Naga coil was excavated from underground at the 'Yagsala Mantapa' or 'Kunbhabhisekham'. The bottom of the one-meter high Naga stone sculpture has a decorated pedestal,which inturn has several other components along with it. Above the main pedestal there is another pedestal or 'Peeta' in the form of 'Koorma'(tortoise),above which rests the five coils of Naga. Vishnu is seated on the topmost coil. The five hoods of the serpent spread like an umbrella over his head.
The Naga sculpture of Thiruvedanthai is 'a unique Naga stone' in the sense that such structures are generally found in the Shiva temple where the Linga seats on the Naga coil. But here the Nityakalyanaswamy temple is a Vishnu temple, where Lord Vishnu lies at the centre of Naga coils. Vishnu is seated at 'Sukhasana' (relaxed posture). The relic of Vishnu has four arms holding a 'Sankha' (conch), 'Chakra' (wheel), a stylized 'Gatha' and a 'Padma' (lotus). The sculpture belongs to the Vijaynagara period as is indicated by its many features like the cylindrical 'Kreeta', elaborate ornaments and the posture of holding of the weapons. The serpent's five hood has 'Mukhapattika' or ornaments in the forehead. The hoods of the serpent have very prominent eyes. This finely executed sculpture is made out of a single piece of greenish granite and its finish is excellent.