Acala, the immovable, is one of the wrathful protective deities of esoteric Buddhism, and in Japan, where he is known as Fudo Myoo, he is the chief of the Five Wisdom Kings (Myoo, Sanskrit Vidyaraja). He is depicted with a fierce, scowling face, his body blue-black, one fang pointing up and one down, holding an upright sword in one hand and a coil of rope in the other, seated or standing on a mass of rock within a surrounding wall of flame. Each element expresses his function. He does not move, the tradition explains, not because he cannot but because he will not, he is the unshakeable resolve of the awakened mind, immovable in the face of every obstacle and temptation.
The sword cuts through ignorance and delusion; the rope binds and drags the obstinate toward liberation, catching those who resist the teaching; the flames burn away defilements; and the rock is the firmness of his vow. His wrath is not anger in the ordinary sense but compassion in a forceful mode, the fierce energy that removes what stands in the way of awakening, and he is understood as a manifestation of the cosmic buddha Vairochana (Dainichi) in his aspect of implacable resolve. Fudo is among the most popular deities of the esoteric Shingon and Tendai schools in Japan, invoked for protection and for the burning away of hindrances, and he is also known in the Tibetan tradition. He shows how Buddhism could turn the imagery of terror to the service of compassion.