Wikipedia
Thantri or Tantri is the Vedic head priest of Hindu temples in Kerala and a very few temples of coastal Karnataka in southern India. It is a position held hereditary. It is the thantri who installs the idol of the deity, and from that moment he assumes the position of the guru of the deity. The thantri has the final word on the rites and rituals of the temple.
Thantris Shrauta are Namboothiri Brahmins who study tantras, and belong to Poorva Mimamsa one of the 6 schools of thought in Hindu philosophy. Poorva Mimamsa deals with the early parts of the Vedas. Another famous school of philosophy is Vedanta also known as Uttara Mimamsa, which means ( Veda+anta) end of Vedas (essence of Vedas). One common misconception about Vedanta is that writers think that it mostly deals with the later parts of the Vedas. It is the essence which enlightens one in the end is referred as Vedanta and not the physical ending parts.
Thantris have the sole right to conduct certain core rituals in temples of Kerala and Tulunadu. In temples like Sabarimala, the presence of thantri is needed every day.
The daily rituals in Kerala temples are traditionally performed by Namboothiris, and often by Embranthiri migrants from the neighbouring Karnataka. Even among Namboothiris, only certain designated families deserve to become "Thanthris". Thanthris have to perform the incredible task of transferring ("Aavaahanam") the aura ("Chaithanyam") of deity and energizing the idol. The techniques employed are described in the "Aagamams" .
The first step of a "Yajamaanan" (a person who has prepared himself mentally and financially) to build a temple, is to seek and accept ("Varikkal") an "Aacharyan" (Guru, Thanthri). "Thanthra Samuchayam" (Granthham) identifies an ideal Aachaaryan as one who "is born into a high class Braahmanan family, has performed all the "Shodasakriyas" (click: "Shodasakriyakal") from "Garbhaadhaanam" to "Agnyaadhaanam", has understood the concepts contained in the Vedams and Aagamams (Braahmacharyam, Gaarhasthhyam, Vaanaprasthham and Samnyaasam), has received blessings and Manthram advice from Gurus and elders, is an expert in performing rites and rituals (Karmams), is capable of receiving spiritual powers through meditation and penance ("Thapas"). Future Aachaaryans of the temple must be descendants of this Guru or Thanthri
During the evolution and development of Thaanthric philosophy, two kinds of Aachaaryans emerged - the Theoreticians and the Practitioners. While the former developed concepts and prescribed procedures, the latter perfected their performance through strict discipline, leading to the attainment of the expected results. Ancient Thanthris were adept in both aspects.
Granthhams on Thamthram (Treatises)
There have been numerous Granthhams, many of which might have been lost, while most of the surviving ones may be lying unseen and unread in some archive or library. Even the most intelligent scholar cannot, during his entire lifetime¸ learn fully nor even read all the Granthhams on the Thanthram.
The treatises may be divided into three categories - Aagamams (Saivam), Samhithas (Vaishnavam) and Thanthrams (Saaktheyam). Aagamams include Nigamam versions too. The former are Sivan's advice to Parvathy, while Nigamams are spoken by Parvathy to Sivan. Other classifications are regional, like Vishnukraanthaa, Rathhakraanthaa and Aswaakraanthaa, and also like Yaamalams and Daamarams. Usually, all branches of knowledge are dealt with in Thanthra Granthhams.
Even treatises written by Keraleeyans are numerous. The most popular among them is the "Thanthra Samuchayam" by Chennas Narayanan Namboodiripad, who was one among the 18 ½ poets (click for "Pathinettara Kavikal") of the Saamoothiri's court. He consolidated and systematized the scattered literature which had then made its learning and practice quite cumbersome. Written in simple style and understandable by the common man, it covers topics like building of temples, consecration of idols, Kalasams, Uthsavams and Praayaschithams.
There have been several commentaries (Vyaakhyaanams) on it, both in Sanskrit and in Malayalam. The treatise describes rituals related to seven deities, Sivan, Vishnu, Durga, Saasthaavu, Subrahmanian, Ganapathy and Sankaranarayanan The Aagamams of these deities have been condensed, as expressed by the author himself, when he stated "Swaagama-saara-samgrahaal".
Two known commentaries in Sanskrit are "Vimarsini" and "Vivaranam". Later, there have been several translations into Malayalam, of which "Kuzhikkaattu Pacha" by Kuzhikkaattu Maheswaran Bhattathiripad (see box) is the most popular. Works such as "Thozhaanooranushtthaanam" and "Parameswaraanushtthaanam" deal with the same topics, also from Kerala.