horse-headed and ox-headed demons in Buddhist hell
Refers to the two demon attendants, Gozu (ox-head) and Mezu (horse-head), who guard the underworld in Buddhist cosmology. Often mentioned together as a pair.
It is said that Gozu and Mezu stand at the gates of hell.
Those two have scary faces just like Gozu and Mezu.
From Buddhist terminology, combining 牛頭 (gozu, 'ox-head') and 馬頭 (mezu, 'horse-head'). The exact historical derivation is uncertain, but the terms are well-established in Japanese Buddhist lore.