i very recently had good cause, or good enough, to talk about fudo.. so here's a copy & paste.
Fudo is 'the immovable one', or Fudo Myoo, 'immovable wisdom king'.
he is the destroyer of delusion and the protector of Buddhism.
his 'mystic name' is Joju Kongo, meaning literally 'eternal and immutable diamond' i think.
he is a Myoo, (wisdom king) & the best known of the 5.. or sometimes 8. he is the destroyer of delusion and the protector of Buddhism & is also the patron deity of the Yamabushi, ascetic warrior monks who used to very occasionally help the samurai.. but mostly live in solitude on mountains.
he is also counted as one of the 13 buddhas of japan, but is not a buddha. more a protector & servant of buddhism, depicted with 'kurikara', his sword, in his right hand, a rope in his left hand, wreathed in flame, clad in rags,looking angry, with a servants hairstyle & 2 fangs. 1 pointing to heaven, 1 to earth. there is significance to his appearance but i don't wanna bore you lol suffice it to say there's a reason for each attribute & accessory.
he has 2 attendants, Kongara and Seitaku to aid him.
also while he looks mean, he is 'here to help' & kinda bound by compassion.. helps people on the path to enlightenment. his devotees perform fire rituals to him, a ritual involving standing under a waterfall & the epic 1000 day pilgrimage or Sennichi Kaihougyou around Mt. Hiei reciting his mantra & visiting various holy sites.
Fudo is the japanese version of Acala.
Acala is present in indian Vajrayana buddhism, Fudo in Shingon & a few others i think. Acala is also the name of the eighth of the ten stages of the path to become a bodhisattva.
not quite complete but not too shabby either 