Agni: Transformative Fire | How to Develop the Bandhas
Shatkarmas and Asana purify the body. They build awareness. Awareness sharpens the senses. Regulating the breath increases our ability to produce the agni.
bandha
Siddhi: Attaining Psychic Powers: A Gift or A Trap? | Hatha Yoga Pradipika
The subtle body is inherently closed for a significant reason. Once it is made open, the subconscious awakens which in turn emerges our karmas. Hatha Yoga is the most powerful in awakening the kundalini. It is also the most dangerous.