Who Is the Bull Demon King (Niu Mowang)?
Eldest of Wukong's sworn brothers
The Bull Demon King is a bull demon in Journey to the West and the eldest of the seven demon kings who swore brotherhood with Sun Wukong.
Around the time he obtains the As-You-Will Staff, Wukong starts mixing with demon kings from many places and becomes sworn brothers with the Bull Demon King, the Flood Dragon King, the Roc Demon King, the Lion-Camel King, the Macaque King, and the Yurong King. In Chapter 3 of the original novel, the Bull Demon King is only mentioned by name and does not play a major role.
He takes center stage later in Journey to the West, fighting Wukong fiercely at the Flaming Mountains over the plantain-leaf fan owned by his wife, the Rakshasa Woman (Princess Iron Fan). His son, Red Boy, also appears as a demon who torments Tripitaka and his disciples.