Mahākāla is a deity common to Hinduism, Buddhism and Sikhism. According to Hinduism, Mahākāla is the consort of Hindu Goddess Kali and most prominently appears in Kalikula sect of Shaktism.Mahākāla also appears as a protector deity known as a dharmapala in Vajrayana Buddhism, particularly most Tibetan traditions, in Tangmi (East Asian Esoteric Buddhism) and in Shingon (Japanese Esoteric Buddhism). In Sikhism, Mahākāla is referred to as Kal, who is the governor of Maya.

According to Shaktisamgama Tantra, the spouse of Kali is extremely frightening. Mahakala has four arms, three eyes and is of the brilliance of 10 million black fires of dissolution, dwells in the midst of eight cremation grounds. He is adorned with eight skulls, seated on five corpses, holds a trident, a drum, a sword and a scythe in his hands. He is adorned with ashes from the cremation ground and surrounded by numbers of loudly shrieking vultures and jackals. Among his side is his consort Kali and they both represents the flow of time. Both Mahakala and Kali/Mahakali represents the ultimate destructive power of Brahman and they are not bounded by any rules or regulations. They have the power to dissolve even time and space into themselves and exist as Void at the dissolution of the universe. They are responsible for the dissolution of the universe at the end of Kalpa. They are also responsible for annihilating great evils and great daemons when other gods, Devas and even Trimurtis fail to do so. Mahakala and Kali annihilates men, women, children, animals, the world and the entire universe without mercy because they are Kala or Time in the personified form and Time is not bound by anything and Time does not show mercy, wait for anything or anyone.

Mahākāla is typically black in color. Just as all colors are absorbed and dissolved into black, all names and forms are said to melt into those of Mahakala, symbolizing his all-embracing, comprehensive nature. Black can also represent the total absence of color, and again in this case it signifies the nature of Mahakala as ultimate or absolute reality. This principle is known in Sanskrit as "nirguna", beyond all quality and form, and it is typified by both interpretations.

All schools of Tibetan Buddhism rely on Mahākāla. He is depicted in a number of variations, each with distinctly different qualities and aspects. He is also regarded as the emanation of different beings in different cases, namely Avalokiteśvara  or Cakrasaṃvara. Mahākāla is almost always depicted with a crown of five skulls, which represent the transmutation of the five kleśās (negative afflictions) into the five wisdoms.

The most notable variation in Mahākāla's manifestations and depictions is in the number of arms, but other details can vary as well. For instance, in some cases there are Mahakalas in white, with multiple heads, without genitals, standing on varying numbers of various things, holding various implements, with alternative adornments, and so on.