Scholars and the traditions themselves distinguish a "right-hand" tantra, whose practice is symbolic and remains within conventional purity rules, from a "left-hand" tantra that ritually employs the very things ordinary religion forbids, in the classic list, meat, wine, and sexual union among them, as a controlled transgression by qualified initiates under strict guidance. Even where such rites exist they are a restricted and guarded minority of tantric practice, hedged with initiation, secrecy and discipline, and much of the tradition treats the transgressive elements as inner and symbolic rather than literal.
Tantra transformed both of its host religions. In Hinduism it deeply shaped the worship of the Goddess and of Shiva and the whole temple and mantra culture that followed. In Buddhism it became the Vajrayana, the tantric vehicle that is the mainstream of Tibetan Buddhism and a major strand of Japanese Shingon, with its deity yoga, mandalas and empowerments. Across both, the constant is that tantra is a path of initiated ritual power, transmitted living from teacher to student, and not reducible to any one of its elements.