According to Tantra, the ultimate truth is the union of Shiva and Shakti. Shiva represents pure consciousness which is inactive (the static energy), while Shakti represents the world force, the kinetic energy of the concrete universe. This notion of the male being identified with the inert, the passive, is brought out in the theme of Shiva being the goddess' mattress or her foot stool. The feminine principle of Shakti, personified as the Goddess Devi is the supreme principle of the universe, which includes both the spiritual and the material.
Depicted as one of the ten Mahavidyas (Great knowledge goddesses), the Devi is shown here as Tara, the second Mahavidya. The Mahavidyas are Tantric deities who represent the ten paths to transcendental knowledge. Various texts describe Tara as standing or seated upon either a corpse or the recumbent Shiva. In this image, Shiva identifiable by his third eye, lies calm and untroubled. Fires in the background evoke the cremation ground with which Tara is associated. Cremation grounds are liminal spaces; bridges between the world of spirits and the world of the living. As such they are powerful locations in which deities and spirits can most directly transfer energies and powers to devotees.
The severed head signifies the end of one cosmic cycle, and waters flowing from the hair of Shiva represents the start of the new.