Legend says that the goddess Kali (a form of Parvati) moved here after losing to the god Shiva in the celestial dance contest.
In order to resolve thus, they performed a dance program at Chidambaram in front of Vishnu, Brahma and other deities.
[1] Shiva performed the Urdhva Tandava posture, i.e. raising one leg above his head and challenged Parvati to replicate it.
Parvati in anger assumed her ferocious form Kali and left Chidambaram (Thillai) and settled outside the town borders.
In the east-facing shrine, the goddess appears in her ferocious form called Thillai Kali.
[2] Kali or Durga worship, also known as Shaktism, entered into Tamil country from Gauda region (present day Bengal) before 7th century C.E.
and his son Kulothunga-II and grandson Rajaraja-II the transition to Saivism was complete and Shaktism was relegated to subordinate role.