Nyasa is accompanied by a specific mantra. The Nyasa are of various types. Jiva-nyasa follows bhuta-shuddhi. After the purification of the old and the formation of the celestial body, the sadhaka proceeds by jiva-nyasa in order to infuse the body with the life of Devi. Thereafter he places the eight Kula-kundalini in several places and chants a mantra. Then the sadhaka becomes devata-maya. After dissolving the sinful body a new Deva body is made and infused with the life of the Devi. He proceeds to matrika-Nyasa.
The bodies of the Devata constitute the fifty matrika. The sadhaka sets him mentally in the six chakras. He places his hand on different parts of his body. First the inner disposition starts which is followed by the external disposition. According to the Tantra-sara, matrika-nyasa has four classifications: kevala; vindu-sangyuta; sangsarga and sobhya.
Rishi-nyasa is done for the attainment of the chatur varga. Mantra is assigned to the head, mouth, heart, anus, the two feet and in general the entire body.
After this follow the anga-nyasa and kara-nyasa. Both are the forms of shad-anga-nyasa. Hridayadi-shad-anga-nyasa is when shad-anga-nyasa is performed on the body. Angushthadi-shad-anga-nyasa is when done with the five fingers and palms of the hands only. Shadanga-nyasa mantras are used on the body for Kara-nyasa, in which they are assigned to the thumbs, the index fingers, the middle fingers, the fourth, little fingers, and the front and back of the palm. This stimulates the nerve centres.
In Pitha Nyasa the Pitha is established in position of the matrika. The pitha is Kama-rupa. Mahashodha nyasa is where a sadhaka places planets, constellations, sacred sites and on her or his body.
Nyasa is used in effecting the proper distribution of the Shaktis in proper positions in order to avoid discord and distraction in worship. Nyasa is necessary for the production of the desired state of mind and its purification. This is the essential principle and rational basis of all this and similar Tantric sadhana. Nyasa divinise the body of the worshipper.