« All the Siddhas are a group of mystics who revolt against caste and rituals and the established order of religion. They are no doubt bhaktas but their bhakti is of a different type. They are very critical of the practice of religion but always hold fast to the one Supreme God and pray for His Grace. Their revolt is only in the manner of their criticism and the challenge they throw to orthodoxy. They are generally against idol worship and they emphasize the worship of God in the heart. Except few, all the Siddhas have been Śaivas.
Based on their aims, Siddhas are classified under three broad groups viz.,(i)the Sanmārga Siddhas,(ii) theÑāna siddhas and (iii) the Kāyasiddhas. However, there is also another group forms the fourth one, who are ‘a few siddha-like’ poets who have been appended to the Siddha school by posterior generations, or who called themselves cittar or Siddhas without properly belonging to the esoteric group itself. »
( Siddha cult in Tamilnadu, its history and historical continuity, R. EZHILRAMAN, 2015, University of Pondichery)
Vâhana 