Ila also called as Sudyumna is mentioned in the Puranas as the son of Lord Manu, the mind born son of Lord Brahma. Ila is an ancient ruler of the Lunar dynasty. He is also mentioned in the Vedas, and his son was Pururavas.

Ila was actually born as a male, but due to a curse, he was transformed into a female. Then due to the powers of Sage Vasishta, in a month, for fifteen days, he appeared in the form of a male, and in the next fifteen days, he appeared in the form of a female. Once when Ila took the form of female, she roamed in a dense forest, and there she saw Lord Budhan, and both of them were married, and they had a son, who was known as Pururavas. Ila was mentioned in Ramayana and in Mahabharata also. In some Navagraha temples, Ila can be seen seated with her consort Lord Budhan.  Ila performed meditation and fire sacrifices and pleased Lord Shiva, and as a result, Shiva had granted him the boon of permanently becoming of a male person. After happily living his life for many years, through the blessings of Lord Shiva, Ila had attained salvation, and then, Ila’s son Pururavas ruled his kingdom in an efficient manner.   Similar to Aravan, Ila can also be worshipped by the transgender people in order to fulfill their wishes. The entire life history of Ila was mentioned in the Bhagavatham. It is believed that those who read the life history of Ila, would be relieved from their various doshams, and would prosper in their life. 

Sri Swetharanyeswarar Temple is an ancient Shiva Temple, and it is situated at Thiruvenkadu, and in that temple, there is a separate shrine for Lord Budan and he can be seen along with his consort Ila. This is a famous Budhan temple, where Lord Budhan once visited this temple, performed puja to Lord Shiva, and received various boons from Lord Shiva.