The 18 Siddhas
A little was known about Siddhas and their Kriya yoga tradition. The Siddhas number about 18 and were concentrated in many part of India, more particularly in present Tamil Nadu, still influencing the entire universe. They attained a state of perfection called as "Soruba Samadhi". The state of perfection, which the Siddha Yogis or the Yoga Siddhas have attained, is due to their penance, magnanimous in selfless contributions and their unique life style. For the Siddhas addressing Shiva, Krishna, Vishnu, Shanmuga, Shakthi or Christ, or Allah so on and so forth are one and the same.
Shiva Purana describes the way Lord Shiva meditates on Mount Kailash since time immemorial. Shiva is worshipped by the Yogis as Lord, and by all the Gods as the supreme Lord. It is said that the history of the Siddha tradition has begun millions of years ago. Lord Shiva initiated Parvathi Devi into Kriya Kundalini pranayama, the scientific art of mastering the breath, in a huge cave at Amarnath in the Kashmir Himalayas (Ramaiah, 1968, p. 108). Siddhas are those who concentrate and hold their breath in the mooladhara, navel, heart, middle of stomach, neck, hairs and raise the Kundalini power.
Later Yogi Shiva initiated others, including the Siddhas Agastya, Nandi Devar and Thirumoolar on Mount Kailash. Subsequently Agastya initiated Babaji into Kriya Kundalini pranayama.
The ancient Siddhas had realized that the divine would also descend further into lower planes of consciousness viz., the intellectual, mental, vital, and physical bodies. They become the virtual embodiment of the ultimate Divinity. Such a state is very difficult to be conceptualized by our limited intellect. The Siddhas discovered that through a complete surrender of their being, their ego, and their very lives, the Divinity would in some exceptional cases descend and completely transform them down to their very cells. This transformation was speed up by the intensive practice of various Kriyas, including hatha yoga asanas, meditation, mantras and bhakti yogas, but above all the Kriya Kundalini Pranayama.
According to the traditions and in particular, there are eighteen Siddhas who attained perfection, which included their spiritual, intellectual, mental, vital and physical bodies. The names of these eighteen Siddhas vary according to different sources. This could be due to the fact that each is given the name of the place where they have attained the state of perfection and also it was customary to call them in several names as was in practice since several centuries.
Apart from these eighteen Siddhas, popularly known as "Pathinettu Siddhargal", there are many others like Konkeyar, Punnakeesar, Pulastiyar, Poonaikannar, Pulipanni, Kalangi, Aluganni, Agapaiyer, Theraiyar, Roma Rishi, and Avvai.
A state of being one with the universe and bringing back the universe within themselves is an act only possible for elevated souls. Siddha means an adept or one who attained perfection or "Siddhi". The 18 Siddhas attained perfection, which included their spiritual, intellectual, mental, vital and physical bodies.
Just as a salt doll dissolves and merges into the oceans, the Siddhas have thrown their personality into the ocean of God or the ultimate reality within, and experienced a progressive transformation of their intellectual, mental, vital and physical sheaths. Thus a divine transformation of their entire human nature takes place after attaining such a unique realization.
This unique realization is possible only through the Grace of God and the techniques used by the Siddhas to prepare their flesh and lower bodies for the descent of the divinity. These techniques are collectively known as Kriya Yoga Siddhantha.