FUDŌ, the "Immovable One" (Skt. Acala, also Acalanātha Vidyārāja), is one of the most popular esoteric Buddhist deities in contemporary Japan. Fudō is most frequently colored black or dark blue and portrayed as sitting or standing on a large stone which, according to the commentary by Śubhākarasiṃha (637–735), represents both the heaviness of the obscurations (Skt. kleśa) and the immovability of the thought of awakening (Skt. bodhicitta). This ambiguity is typical of tantric thought in which the obscurations are non-dually identical with awakening (Jpn. bonnō soku bodai).

Fudō is encircled by flames that are produced by his state of concentration. These flames themselves are described as being "garuda-headed," that is, shaped like the head of the mythic garuda bird, said to be able to eat snakes without harm. For this reason, the garuda is taken as a symbol of...