Batou Kannon by Aya Kato

So says JAANUS:

"The "Horse-headed" Kannon (Kwannon, Kwan Yin) in an angry, funnu, form. He is also considered to be the angry form of the Buddha Muryouju, one of the Six Kannon who saves those in the [Buddhist] realm of animals...

"He is distinguished by the white horse's head that he wears like a crown. The horse is one of the symbols of dominion of the 'ideal king,' Kyouryourinjin (or Kyouryoujouou; Sk: Chakravartin). There are many different forms of Batou having one to three faces and two to eight arms, and he holds different attributes in different images.

"Many stone statues, sekibutsu, of Batou were once set in place to protect travelers and their horses from injury on dangerous paths. It is also thought that Batou became conflated with a folk horse deity believed to be the vehicle of a deity who rides between this world and the sacred realm. Because of this identification, he became the protector of horses and the Buddhist counterpart, honjibutsu, of deities of common Komagata (lit. "Horse-shaped") shrines, which are found all over Japan."