Agastya, in Tamil Hindu traditions, is considered as the first and foremost Siddhar (Tamil: cittar, Sanskrit: siddha). A siddhar is derived from the Sanskrit verbal root sidh which means "to accomplish or succeed". As the first Siddhar, Agastya is deemed as the first master, accomplished, the sage who perfected his knowledge of the natural and spiritual worlds. This Tamil concept has parallels to Tibetan mahasiddhas, Sri Lankan Buddhist, and Nath Hindu yogi traditions of north India.

Nandi Devar is one of the foremost of the 18 yoga siddhas. He has been directly initiated by Lord Shiva Himself. And so it is no wonder that he initiated some spiritual giants as his disciples such as Thirumoolar, Patanjali, Dakshinamoorthy, Romarishi & Sattamuni. His main contributions include medicine, kaya kalpa & Alchemy.

Both the life and works of Thirumoolar Siddhar are extremely important for the Tamil Shaivism and Siddha tradition. It is our absolute blessing that we have access to these texts. Siddha Thirumoolar’s Thirumanthiram unfolds the most profound and subtle realizations of a phenomenal Siddha. It is revered as Siddhantha – “the end of ends”.

Legend has it that Thirumoolar was immersed for years in deep samadhi. Some accounts say the Siddha was in a cave and others say the Siddha sat under an Arasa Maram (Peepal Tree). At the end of each year of his continuous and great samadhi, he would come out to scribe a single verse with a stylus on a palm leaf, capturing in that verse the sum of one year’s meditations. Since he wrote over 3000 verses, this would mean he lived over 3000 years. There are other accounts that say Thirumoolar Siddhar wrote a single verse each day for 3000 days. Whatever actually happened, we believe that even a year’s meditation would be insufficient to comprehend the subtle and complete jnana (realized knowledge) contained in the four-line stanza of each verse in Thirumanthiram.

Bhogar was a South Indian by birth, belonging to the caste of goldsmiths, who became a siddha purusha under the guidance of Kalanginaathar. In Bhogar's Saptakanda he reveals details of various medicinal preparations to his disciple Pullippani (so named as he is believed to have wandered in the forests atop a puli or tiger) and at every stage he quotes his guru as the authority. Also Pulippani must have been a young man then, as he is often referred to as a balaka.

Sri Konganavar (Konganar/Gonganar/Gonganavar)- is one of the 18 yoga siddhas initiated by Boganathar. His contributions include 25 known works in medicine, yoga, philosophy, religion etc. Sri Konganavar is a great Siddha and a compassionate Guru. He has over 557 disciples!!!. He is so compassionate and reaches out to fulfill the material needs of his disciples and so as the crowd.

Machamuni is a siddhar. He was the child brought up by Pinnakeesar. He is also Pinakeesar's disciple. There is a story that once Lord Siva was preaching Uma Devi. Uma Devi had slept when Lord Siva was preaching her. However, a fish was listening to the lecture. Later on that fish was transformed into Siddhar Machamuni by Lord Siva.

Goraknath is one of the 18 yoga siddhas in the 'nath' tradition. He was initiated by Dattatreya (Vishnu), Macchamuni, Allama Prabu. Some of his contributions include "Avadhuta Gita" and 13 other works, order of ascetics, medicine, alchemy, Hatha yoga pradipika classic etc. He has attained samadhi at Poyur (Girnar).

In the annals of Siddha History Sattaimuni Siddhar occupies a vital place for his anthropological work. Sattaimuni Siddhar was born in Srilanka and was living with his family as a mendicant friar outside a temple. He also gained knowledge from Siddhar Agathiyar and Siddhar Bogar. Sattaimuni Siddhar is expert in Siddha rejuvenation medicine science and his “Sattaimuni Karpam -100” is followed by many even now.

Sri Sundaranandar is the disciple of siddhar Sattamuni. It is believed that he got the Siva Linga of siddhar Agastiar, established it in Saduragiri and worshipped it. Saduragiri Sundara Mahalingam temple comes under the Thaniparai area of Saptur reserve forests in Tamil Nadu. It is located in Watrap, Viruthunagar district. Srivilliputtur is the big city located near Saduragiri. For thousands of years, realized sages and siddhars lived there worshipping the Siva Linga called " Sundara Mahalingam ". " Sundaram " means, the handsome One, " Maha " means great and lingam means " Siva, the Supreme Self ".

Ramadevar or Uromarishi or Yacob Siddhar is a great siddhar who occupies a distinct and significant part in the Tamil Siddha Medicine System for his discoveries in all the spheres of Siddha Science. An eminent thinker and lively researcher, was well known for his simple usage of Tamil language to describe extraordinary concepts in Siddha Science. Bogar in his biographies about Siddhas says, he was born in a Brahmin family. The guru of Ramadevar Siddhar is the great Siddhar Pulasthiyar. After entering into the world of Siddha science, Siddhar Ramadevar by the dint of his deep meditation techniques awakened his kundalini energy. He succeeded in bringing the energies through the chakras up to the crown and united with the Divine for long. He attained perfection in Attama Siddhis and said to have performed many miracles called Jaalam in Tamil.

Kudambai is one of the female Siddha of the 18 Siddha traditions who are known for their affiliation to great works in medicine, alchemy, philosophy, religion. She, attained soruba samadhi in Mayavaram or Mayil-aadu-durai. Mayavaram in Tamil means, a place for deathless boon. As this lady attained Immortality or soruba samadhi here. Mayavaram is also known as Mayil-aadu-durai meaning, a place where the peacock dance in ecstasy. Peacock is a symbol of Lord muruga. Here by the grace of Lord Muruga kudambai attained Immortality.

Karuvoorar Siddhar was born in a place called Karuvoor of the then Chola Kingdom, what is now called as Karur. Literary research works pose multiple theories about Karuvoorar Siddhar’s birth and origin. Some consider that, he is also called as Karuvoor Devar. Some postulate that Karuvoorar Siddhar should have been born to a family of Sthapathis or idol architects. For this theory the reference provided is from Chapter 4 Verse 452 of “Agastyar 12000” a composition by the great Sage Agastya Muni Siddhar.

Sri IdaiKadar is one of the 18 renowned siddhars of Tamil Nadu and is considered an incarnation of Lord Vishnu. He is from the region of Thiruvannamalai. Thiruvannamalai is one of the Pancha Bootha Sthalams (Five Temples where Lord Shiva is represented by each of the Five Elements). In Thiruvannamalai, he is worshipped as Fire element. His exact era of living is not known precisely yet. But it seems he was born on some time back in 2nd – 3rd century BC and he lived for around 600 years. Also, he seems to be from Yadhava (One of the oldest Indian community from which Lord Krishna was born) community by seeing his profession and most of his songs.

Kalangi Nathar was the guru of Siddhar Bhoganathar or Bogar and a direct disciple of Siddhar Thirumoolar. He is one among the seven disciples whom thirumoolar transcended his knowledge. The other six being -Indran, Soman, Rudhran, Kanduru, Brahman and kanjamalaiyan.

Valmiki is one of the 18 yoga siddhas. He was initiated by the great sage Narada. He is very much known for recording the epic work ‘The Ramayana’. He has attained samadhi at Ettikudi.

Pathanjali is one of the 18 yoga siddhas. He was initiated by Nandi Devar. He is known for his works on yoga sutras classic. He has attained samadhi at Rameswaram. He is also known as father of yoga.

Dhanvanthri is one of the 18 yoga siddhas. He is known for his contributions on medicine, alchemy, kaya kalpa, 22 known works. He has attained samadhi at Vaideeswaran Kovil.

Paambatti is one of the 18 yoga siddhas. He was initiated by Sattamuni. His contributions include siddha philosophy. He has attained samadhi at Harsankaran kovil. He was originally a snake charmer before he met his guru Sattamuni. Later after being initiated by his guru, due to his intense sadhana he has become a siddha.