Hayagriva, the name means horse-necked, is a wrathful deity of Mahayana and Vajrayana Buddhism, recognised by the small horse's head, green or white, that emerges from the flaming hair above his own fierce face; his defining attribute is his neigh, said to be so terrible that it terrifies and scatters the forces that obstruct the teaching and the practitioner. The name and the form are taken over from Indian material, where Hayagriva is a figure of some antiquity, in the Hindu tradition a horse-headed form associated with Vishnu and with the recovery of the Vedas, and Buddhism adapted the horse-necked power to its own ends, making Hayagriva a wrathful protector. In the developed Vajrayana scheme he is understood as a fierce manifestation within the lotus family of Amitabha and is closely linked with Avalokiteshvara, the bodhisattva of compassion, so that, characteristically, the terrifying form is the compassionate one in an active, obstacle-destroying mode, wrath in the service of liberation rather than of harm. He is invoked especially against illness, hostile forces and hindrances to practice.
Hayagriva travelled widely across the Buddhist world: he is important in Tibetan and Mongolian Buddhism as a protector, and in Japan he appears as Bato Kannon, the horse-headed form of the bodhisattva of compassion, where he became, among other things, a protector of horses and of animals. The horse's neigh cutting through obstruction is his enduring signature.