Ma Mien Concept Picture

Ox-Head (Simplified Chinese: 牛头; Traditional Chinese: 牛頭; Pinyin: niú tóu) and Horse-Face (Simplified Chinese: 马面; Traditional Chinese: 馬面; Pinyin: mǎ miàn) are two fearsome guardians of the Underworld in Chinese mythology, where the dead face judgement (and punishment) prior to reincarnation. As indicated by their names, one has the head of an ox, and the other has the face of horse. They are the first people a dead soul meets upon arriving in the Underworld; in many stories they directly escort the newly dead to the Underworld. Usually, the two are mentioned together (牛头马面/牛頭馬面
In the Chinese classic novel Journey to the West, at one point Horse-Face and Ox-Head are sent to capture Sun Wukong, the Monkey King. Sun Wukong overpowers both of them and scares them away. He then breaks into the Underworld and crosses out the names of himself and his people from the record of living souls, hence granting immortality to himself and his monkey followers.
R:RotG Loki Initial Concept
Ma Mien Concept
Hades Squad
Rape of Persephone