The story of Purushamriga and Bhima is found in Tamil folklore. Purusha Mrigas are short statured half man half animal divine beings who are devotees of Mahadev Shiva. They are found on the walls of major Shiva temples in South India, especially in Tamil Nadu.
Pandavas decided to perform the Rajasuya Yagna in Indraprastha. Yudhisthira, the eldest of the Pandavas asks, his four brothers to take the blessing of neighboring kingdoms.
During his journey, Bhima, the second of Pandava brothers, meets Bajrang Bali Hanuman. After a short interaction, Hanuman plucks out three strands of hair from his tail and gives it to Bhima and reminds him that he will need them during his journey. Bhima then arrives at the kingdom of Kuber and there in a garden he spots a Purushamriga. Only a true devotee of Mahadev Shiva can see a Purushamriga.
Bhima invites the Purushamriga to the Rajasuya Yagna and asks him if he would guard the entrance of the Yagna.
Purushamriga but told Bhima that he moves at the speed of thoughts. His sole purpose in life is to meditate on Shiva. So Bhima will have to move in a greater speed. If Bhima blocks his path and breaks his meditation he would devour him.
Bhima thought that he would be able to outrun the short-statured half-man half-animal divine being to Indraprastha. So he agrees to the condition set forth by Purushamriga.
But soon Bhima realizes that he will not be able to outrun the Purushamriga.
Bhima then remembers the gift of three strands of hair given to him by Hanuman. To save his life, Bhima throw one strand of hair down. When the hair touched the ground a million Shivlings appeared there.
Purushamriga suddenly halts and then performs pujas to each of the million Shivlings and before running to Indraprastha.
Thus Bhima uses all the three strands of hair to slow the Purushamriga.
But the Purushamriga catches Bhima on the boundary of Indraprastha. But luckily one foot of Bhima was in Indraprastha and the other foot outside. Purushamriga catches hold of the foot which was outside Indraprastha.
Yudhisthira arrives at the scene and listens to the contract entered by Bhima and Purushamriga. Yudhisthira then tells Purushamriga that the leg of Bhima that is not in Indraprastha belongs to him and he can devour it. But the leg in Indraprastha is of Bhima’s and that cannot be touched.
Purushamriga quickly releases Bhima and tells Yudhishthira that he was testing him - Yudhisthira was indeed a true Dharmaraja as he did not tweak the law to protect his brother.
Purushamriga also thanked Bhima for giving him the opportunity to worship millions of Shivlings. He also praised the speed and agility of Bhima.
Purushamriga helped the Pandavas in the successful completion of the Rajasuya Yagna.
Then on the advice of Bhagavan Sri Krishna, Purushamriga went to Chidambaram Temple to guard the entrance of the temple.