In Tantric Buddhist traditions there are two kinds of deities shown as wrathful in appearance with flaming hair, bulging eyes, open mouths showing fangs, and garlands of severed heads. One of these kinds Includes enlightened beings that assume fierce appearances to remove obstacles or perform other protective functions. Though they may look like demons, these deities are said to be wrathful manifestations of wisdom and method. The other variety of these ferocious looking figures includes unenlightened, indigenous gods that were incorporated into Buddhism and bound by oath to protect a tradition or lineage of tantric teachings.
In non-Tantric traditions of Mahayana Buddhism, these beings are protector deities who destroy obstacles to the Buddhas and the Dharma, act as guardians against demons and gather together sentient beings to listen to the teachings of the Buddhas. In Tantric Buddhism, they are considered to be fierce and terrifying forms of Buddhas and Bodhisattvas themselves. Enlightened beings may take on these forms in order to protect and aid confused sentient beings. They also represent the energy and power that is needed in order to transform negative mental factors into wisdom and compassion. They represent the power and compassion of enlightened activity which uses multiple skillful means [upaya] to guide sentient beings as well as the transformative element of tantra which uses negative emotions as part of the path. According to Chogyam Trungpa, »wrathful yidams work more directly and forcefully with passion, aggression, and delusion-conquering and trampling them on the spot.«
In Tantric Buddhist art, these fierce deities are presented as terrifying, demonic looking beings adorned with human skulls and other ornaments associated with the charnel ground, as well as being often depicted with sexually suggestive attributes.