Mezu.

Mezu (馬頭) is the horse-headed counterpart to Gozu, a powerful oni-like demon whose animal face marks him as something beyond the human and beyond pity. The long muzzle and rigid neck lend the figure a harsh, driven energy, as though he were made to pursue, herd, and overtake the dead without pause. In art he belongs to the same infernal order as Gozu, but the horse head gives him a more forward, relentless force.

Mezu meets souls as an officer of the underworld. He stands among the first terrifying beings of hell, seizes the condemned, and ensures that punishment proceeds without escape or delay. In popular explanation he and Gozu are sent after any spirit foolish enough to try to flee. Mezu's role is therefore not abstract judgment, but custody and pursuit.

Like other animal-headed wardens of Buddhist hell, Mezu came into Japan through the transmission of Indic and Chinese underworld cosmology. Japanese religious imagination localized these beings inside the courts of Enma and the vivid postmortem world preached in temples and pictured in scrolls. Mezu became memorable because the horse-headed form is visually immediate and because he is always paired with Gozu as one of hell's principal enforcers.