Agastya is one of the saptarishis who are extolled at many places in the Vedas and a revered Vedic sage and earliest Siddhar. He is also believed to be the author ofAgastya Samhita. Siddhar were spiritual adepts who possessed the ashta siddhis, or the eight supernatural powers. Sage Agathiyar is considered the guru of all Siddhars, and the Siddha medicine system is believed to have been handed over to him by Lord Muruga, son of the Hindu God Lord Shiva and Goddess Parvathi. Siddhars are the followers of Lord Shiva. Agathiyar is the first Siddhar. His disciples and other siddhars contributed thousands of texts on Siddhar litratures, including medicine and form the propounders of the system in this world. He is considered as the Father of Tamil literature and compiled the first Tamil grammar called Agathiyam. It is believed that he has lived in the 6th or 7th century B.C and specialized in language, alchemy, medicine and spirituality (yogam and gnanam). There are 96 books in the name ofAgathiyar.
Sage Agastya is often considered the father of traditional Indian Medicine among many other streams of knowledge. In his book, he is believed to have given the description of, and instructions for the creation of medicines for many types of fevers, cancer, treatments for impotence, abdominal problems, brain and eye problems, bone problems, etc.
Among the various legends associated with him is that of the Vindhya Mountains. According to a story in the Shri Rama-Charitra-Manasa, at one time, Mount Vindhyachal was continually growing in size due to taunting comments by the Sage Narada. So as to temper the vanity of the mountains, Sage Agastya and his family traveled to South India, via the Mount Vindhyachal. On their way, when the Vindhyas saw Sage Agastya, he bowed with respect and reverence, upon which Sage Agastya, jokingly asked if he would stay bowed and subdued with respect till the sage returned. The Vindhyas was truly benevolent and promised to not grow until the seer's return from the South. After passing through the mountain, sage Agastya told his wife, that they would never again cross over to the North side of mount Vindhyas.
Agastya is regarded as the founder and patron saint of silambam and southern kalaripayat. Shiva's son Murugan is said to have taught the art to Agastya who then wrote treatises on it and passed it on to other siddhar. Dravidian siddha medicine (siddha vaidyam) taught to kalaripayat marmas, chonndu varmam and nokuvarmam practitioners is also attributed to the sage Agastya.