Thiru Thanjai Mamanikoil Divyadesam located on the banks of a river Vennaru, which is a group of 3 temples. Sreeman Narayanan is blessing the devotees in the three different temples as Sri Neelamaga Perumal, Thiru Manikundra Perumal and Veera Narasimha Perumal. These three temples are being collectively worshipped as One Divyadesam. Among the 108 Divyadesam, Thiru Thanjai Mamanikoil is the only Divyadesam where three temples located very nearby are put together worshipped as one Divyadesam.

In Krutha Yuga, three Demons named Thanjagan, Thandagan and Gajamugan had put together underwent a sincere penance towards Lord Shiva. Pleased at the devotion Lord Shiva gave them his Prathyaksham was asked for the boon what they were looking for. Asuras had asked Him for a Boon of Immortality. Lord Shiva advised them that Sreeman Narayanan is the one and only preserver and HE only would be in a position to offer this boon for them and assured them that there would not be to them. After getting the Great Boon from Lord Shiva, the Asuras started troubling the entire universe and they also started harrassing the entire Devas and Rishis. During that time there was a severe drought and famine in the whole universe. But surprisingly there was one and only place with enough food and water and that was Sage Parasar's abode. By knowing this Asuras went down to Sage Parasar’s place and assaulted him. The Sage requested the Almighty to help him out. Finally Lord Paranthaman sent His Sudharshana Chakra and destroyed all the Demons, who were troubling everyone. Only these 3 Asuras were left. Lord Sreeman Narayan appeared before Thanjagan and beheaded him. At last Thanjagan realized all his mistakes and begged the Almighty to Pardon him. Pleased Almighty forgave all his blunders. Hence the place is known as Thanjagan Oor and known as Thanjavur and also as Tanjore. Second Demon Gajamugan took the form of elephant and fought. The Almighty then took the form of Lord Narsimham ( Half Man and Half Lion ) and killed the Demon. Regretted Gajamugan asked to pardon him. From that time the place where Gajamugan was killed is worshipped as Thanjai Yali Koil. ( Yali means Elephant ). The frightened third Demon Thandagan went down to Bhadhaala Logam to escape. Lord took the form of Varaham ( The Pig ) plunged into Bhadhaala Logam and destroed the Demon. The place where Thandagan killed has been known as Thandagaranyam. The Almighty appeared as Bhuvaraha Murthi after beheaded Demon Thandagan is being worshipped as Sreemushnam, one among the 22 Abimana Sthalams, located near Mayiladuthurai. At last Almighty gave salvations to all three Demons.