Heifeng Guai
Heifeng Guai (), also translated as the Black Wind Demon, is a character from the 16th century Chinese novel Journey to the West. He is a demon based in a cave on Black Wind Mountain (黑風山). His true form is a black bear but he appears as a dark-complexioned man armed with a Black Tassel Spear. He steals Tang Sanzang's cassock during a fire. Sun Wukong goes to confront him later to take back the cassock but fails so he seeks help from Guanyin. The Black Wind Demon eventually surrenders to Guanyin after she uses one of the artifacts that the Buddha gave her (similar to the ring on Sun Wukong's head), and becomes the mountain's guardian deity. Journey to the West
During their journey to obtain the scriptures, Tang Sanzang and his disciple encountered the Guanyin Temple. However, they were targeted by Elder Jinchi, a greedy and foolish monk, who set fire to the temple in an attempt to harm them. The Black Bear Spirit went to extinguish the fire but took the opportunity to steal the precious Kasaya robe bestowed upon Tang Sanzang by the Buddha. Sun Wukong engaged in multiple battles with the Black Bear Spirit but failed to retrieve the robe, so he sought help from Guanyin Bodhisattva in the South Sea. Guanyin Bodhisattva transformed into Lingxu, a close friend who was supposed to celebrate the Black Bear Spirit's birthday, and presented an elixir as a gift. The Black Bear Spirit swallowed the elixir, disguised as Sun Wukong, but suffered great pain and revealed its true form. Guanyin Bodhisattva retrieved the Buddha's robe for Tang Sanzang and used the Golden Cincture to bind the Black Bear Spirit, compelling it to convert to Buddhism and become a guardian deity of  in the South Sea. References

Journey to the West characters
Chinese deities
Shapeshifting
Fictional demons and devils