Golden and Silver Horned Kings

The Yellow Horned King (金角大王) and Silver Horned King (銀角大王) are two demon kings who serve as antagonists of the classic novel Journey to the West and its multiple adaptations. They are two boys in charge of watching over Taishang Laojun's furnaces, who escaped to the mortal realm, and based in Lotus Cave (蓮花洞) on Flat Peak Mountain (平頂山). They also appears in the movie Doraemon: The Record of Nobita's Parallel Visit to the West as supporting antagonists.

Personality
Yellow Horned King and Silver Horned King are typical demon kings who capture and eat humans who arrived at their location. They also enjoy Taoism and often doing its alchemy. Both of them are also protective towards each other.

Origins
The two Horned Kings were originally the two servant boys of Taishang Laojun, watched over his furnaces. One day, they escaped into the mortal realm, based on the Flat Peak Mountain, and proclaimed themselves to be two demon kings. Knowing Xuanzang's flesh would grant them immortality or long lifespan, they drew pictures of his party to remember when they came. They also took Laojun's five special items, the Purple Gold Red Gourd (紫金紅葫蘆), Suet Jade Flask (羊脂玉淨瓶), Golden Cloth Rope (幌金繩), Seven Stars Sword (七星劍) and Palm Leaf Fan (芭蕉扇).

Role in the story
When Xuanzang arrived into the mountain, the Silver Horned King managed capture Xuanzang's party, and pin down Sun Wukong under three mountains. Sun Wukong escapes with the help of the mountain deities. Despite multiple defeat, Wukong always managed to escape and rob the demons of their special items, and even killed their godmother (a demonic fox). Wukong then traps the demons in the gourd and frees Xuanzang and the others. Just as they are preparing to continue on their journey, Taishang Laojun appears and tells them the demon kings' true origin, and claims back all the things Sun Wukong took from the demons and brings the boys back to Heaven.

Doraemon: The Record of Nobita's Parallel Visit to the West
Here, they are the servant of the Bull King. Like him and many other Youkai, they escaped from the original novel, helped him and Queen Iron Fan in capturing Xuanzang and eating his flesh. Eventually, they were defeated and sent back to the novel by Doraemon. There is no indication of these two here being Taishang Laojun's servant.