Gyu-mao rules as a powerful demon king within the fiery volcanic peaks of the Flaming Mountains, commanding grotesque demonic followers. His singular goal is to capture the monk Genjo Sanzo (Prince Amat in the English dub) and consume him to extend his own life. To achieve this, he deploys his imp minion Shoryu (Filo Fester) to set traps and sow discord among Sanzo's companions, luring them towards his volcanic domain. Possessing significant power, Gyu-mao can trigger devastating volcanic eruptions that reshape the landscape with impassable lava barriers. He also wields shapeshifting abilities, notably transforming into a terrifying man-faced bull – a visage considered so menacing its depiction was altered for the English release. His wife, Ratsunyō (Queen Gruesome), holds the Basho-Sen, a magical fan capable of freezing lava, making it a key objective for the protagonists. During the clash at the Flaming Mountains, Gyu-mao captures Sanzo and Cho Hakkai (Sir Quigley Broken Bottom), preparing to cook them for a demonic feast. He betrays Shoryu by imprisoning him within a jar, an act that ultimately pushes the imp to aid the heroes. Gyu-mao meets defeat when the protagonists, assisted by the repentant Shoryu, rally against him. Overpowered in combat, he plunges into molten lava only to be frozen solid by the Basho-Sen, now wielded by Cho Hakkai. Gyu-mao's dark-skinned, bull-horned, monstrous demon design directly inspired the character Bowser in Nintendo's *Super Mario Bros.* franchise.