The Kapalika-s (Sanskrit कापालिक) are one of the two main sects of Siva follows, who follow a a non-Puranic or tantric form of Saivism. Some of their members were considered to have written the Bhairava Tantra-s, including the subdivision called the Kaula Tantra-s.
They are called Kapalika-s literally meaning the ‘skull-men,’ because, they carried a skull-topped staff and a cranium begging bowl. Differing from the more respectable Brahmin householder of the Saiva Siddhanta, the Kapalika ascetic imitated his ferocious deity, Lord Siva, and covered himself in the ashes from the cremation ground, and propitated his Gods with the supposedly impure substances of blood, meat, alcohol, urine and sexual fluids from intercourse unconstrained by caste restrictions. Flaunting such rules that were considered impure by the more orthodox Brahmin-s, the Kapalika-s went against Vedic injunctions, and hence were considered a Tantric sect. Their main aim was power through evoking powerful deities, especially the Goddesses.
They also have had a significant influence on Yoga, especially Hathayoga. Evidence of this can be found through texts such as Hathayogapradipika, which list some of their eccentric practices. This apart the main texts of their lineage the Bhairava Tantra and the Kaula Tantra offer many Yogic practices as part of their teachings.
Bhairava Tantra is a key text of of Kashmir Saivism. It is presented as a discourse between Lord Siva and his consort Sakti. The text talks about 112 meditation methods, known as dharanas, which include pranayama, concentration on energy centres of the body, non-dual awareness, chanting, visualisation and contemplation through each of the senses. A an important aspect discussed in these texts is the prerequisite to success in any of the 112 practices, which is a clear understanding of which method is most suitable to the practitioner.
Kaula or Kula describes a kind of Hindu Tantrism, more associated with the Kapalica sect of ascetics. The concepts of purity, sacrifice, freedom, the spiritual master (guru) and the heart are core concepts of the Kaula tradition. Similar to other tantric schools, the Kaula-tantra adopts an approach of positive affirmation, rather than prescribing self limitations and condemning of various actions. Thus it embraces acts such as sexuality, love, social life and artistic pursuits as important domains of spiritual evolution. The main approach of Kaula-tantra is practical methods for attaining enlightenment, rather than merely engaging in complex philosophical debates. The main means employed in the Kaula practice are spiritual family, initiation into rituals, sexual rituals such as maithuna, spiritual alchemy, controlling or energy through mantras and other mystical methods, and the realisation of individual and universal consciousness .
The Kaula lineage is closely linked to the Siddha and Natha traditions. Owing to this fact, their influence on the Yoga tradition was quite significant, as the Natha lineage is an influential lineage of Yoga teaching. It is highly possible that Svatmarama and others in this lineage belonged to the Kaula tradition, and perhaps even to the Kapalika sect. It is perhaps the reason for some of the mysterious practices that form part of texts such as Hathayogapradipika.
Many conservative Yogin-s were disapproving of their methods, and shied away from their practices. Yet the Kapalika-s and their mysterious methods have endured till the current day. Visitors to Varanasi, the ancient and holy city on the banks of the river Ganga, can very often come face to face with such ascetics.