In fact, the Tantras are primarily the scriptures of methods of sadhana - spiritual disciplines (some say there are sixty-four Tantra practices that a sadhaka must master to realize the highest goal). And the ultimate goal is Moksha or Final Liberation from the bondage of ignorance, from the chain of recurring birth and death, through the knowledge of our true self as one with Shiva. The attainment of this knowledge calls for severe austerities, tapas, and spiritual disciplines. The knowledge based on conceptual/theoretical understanding or command over the scripture is not enough, the knowledge must be direct: i.e. the sadhaka must directly experience his/her unity with Shiva-Shakti. Thus, in short, Tantras also lay emphasis on transcendental realization of our true nature as the final aim of spiritual practices.
These sadhanas/disciplines must be undertaken only under the illumining guidance/instructions of a realized soul - The Guru or spiritual Teacher. Undertaken by oneself, these practices might lead to distortion in comprehension and might create mental and or physical ailments. The competent spiritual teacher is one who himself/herself has attained the highest knowledge, and who is holy and pure. He/she can therefore, initiate others into the secrets of spiritual unfoldment.
The Tantras define two types of initiations or Diksha. First, the Shambhavi Dikshais direct enlightenment of the disciple by mere wish or touch of the Guru, and the second one is Mantri Diksha where the Guru gives a mantra to the seeker after Truth. Examples of Shambhavi Diksha are rare as here the Teacher must be of exceptional spiritual powers as Christ, Sri Krishna, or Sri Ramakrishna. We see in the life of Paramhamsa Guru Sri Ramakrishna that he initiated and led to direct realization of higher spiritual consciousness in some of his disciples by writing a mantra on the tongue and also by mere touch, as on 1st January 1886, and by mere mental resolve!
More common is Mantra Diksha, for most of the Gurus and the disciples do not have that highest power to transfer or receive the highest attainment. Mantra is a sacred word, or a formula, which is in fact the name of God. Mantra is one with the chosen deity; name and the named are in fact one. A word and the thought are one. By constantly meditating and repeating the Mantra, the initiate gradually achieves refinement of the inner milieu, and acquires various levels of spiritual powers and experiences. Some examples of the Mantra are 'Om Namo Narayana', 'Om Namah Shivayah', 'Om Saradaya Namah', etc. The chosen deity in the Tantras may be a form the Goddess Mother.
Problems with the Tantras
"It should be noted that there evolved a school of thought amongst the Shaktas known as Vamachara - 'the occult practices'. Its ritual of wine and women, apparently a pure sensualism, gained some notoriety. If, however, we penetrate a little into the meaning of accessories used we shall find no ground for condemnation. The symbols of wine and women were employed in order to teach freedom from lustful passions by trying to see everywhere the Divine Mother. In course of time, it is true, the original spirit of the ritual was forgotten, and degeneration of the whole form of worship ensued. The idea involved was admirable one, but in its application it became dangerous and actually evil." (From 'The Spiritual Heritage of India, by Swami Prabhavananda, Sri Ramakrishna Math Chennai (India) Publication, page - 149)
The reasons for this mystery and secrecy may be found in historicity of development of Yoga practices associated with rituals and rites, including animal sacrifices, through the period of dominance of Buddhism and Jainism. Probably, the banning of ritualistic worships and animal sacrifices etc. forced the sadhakas of Tantra to undertake their sadhana in secrecy, and the mystery soon shrouded their methods and means. Secondly, as with every religious practice, entry of persons of lesser caliber and knowledge, including those who practiced these methods for achieving personal material gains etc., caused the Tantras to degenerate in many instances at the cost of blemish on the system as a whole. The third cause may be the repulsive techniques used in the practice, such as a) meditation in lonely place like burial ground, b) use of animal and human skull, and blood, etc. c) involvement of sexual practices as in sadhana of Veera Bhava, and 4) use of narcotic or similar drugs by the sadhakas.
Spiritual and mental levels of growth vary from person to person; accordingly, the rituals adopted also are different. For instance, those people with dominant animal instincts must avoid all temptations, those in whom human and spiritual tendencies are well balanced may take up practices of heroic -Veera - Bhava, and the pure in the heart should take up the highest sadhana of Divya Bhava or Godly practices.
The people indulging in Vamachara or wine and women practices etc. are like those, if one may say so, who try to enter the Palace through the path of drainage pipes! One would reach the destination, but the route adopted is dirty and dangerous. Sri Ramakrishna says, 'why enter the Mansion from backdoor like a thief? Instead, take the royal road of japa and devotion, which is the right approach to the Golden Gate of the Mansion! One purpose of advent of Sri Ramakrishna on this earth was to establish the authenticity of the Tantras, no doubt, but in addition he showed the simpler and the purer ways to undertake such Tantric sadhanas. He has shown that there is no need to take help of wine and woman; other equally effective but less dangerous methods are available like worship of chosen ideal in the cavity of the heart, repeating Holy name of the deity of our choice, seeing every female as Divine Mother, and association with pure and holy men.
It is also to the credit of Sir John Woodroffe, the Chief Justice of Calcutta High Court under the British India, who undertook monumental work of bringing out worm-eaten palm-leaf manuscripts on the Tantras, and who was engaged in painstaking research of translation culminating in publications of great works on Tantras for the benefit of future mankind.
The concept of Coiled up Energy - the Kundalini Shakti!