Baigujing

The White Bone Demon, also known as Baigujing is an antagonist of the classic novel Journey to the West and many of its adaptations. She was a demon who desired to eat the flesh of Xuanzang.

Past
Not much is known about her past, but it is presumed that she was once a human who transformed into a demon after death.

Role in the story
Upon learned that Xuanzang had arrived to her location, Baigujing disguised herself as a village girl and offered him and his disciples poisonous fruits. However, Sun Wukong used his powers and detected her true identity, and hit her with his staff, seemingly killing her. Having survived the attack, Baigujing dug underground to recover. Baigujing returned a second time disguised as an elderly woman and lied to the group that the village girl from earlier was her daughter. Sun Wukong sees through her disguise once again and kills her. The group is angered at Sun Wukong and continues to not believe him.

She returns a third time as an elderly man who lies about having a daughter and wife that the group believed are her avatars that Wukong previously hit, and taunts Wukong into attacking her by using his powers, and only he could hear her. Having a short-temper, he finally beats her with his staff and kills the demon, revealing that she was just a skeleton spirit.

Sun Wukong shows this to Xuanzang, who initially believes him, but Zhu Bajie convinces Xuanzang that Sun Wukong transformed the corpse into a skeleton to evade the Band-tightening spell. Thus, Xuanzang is angry at Sun Wukong at his reckless slaying and scolds him, and sends him away. Hurt by his master's words, Sun Wukong leaves and returns to Water Curtain Cave. In his absence, Tang Sanzang gets caught by another demon—Yellow Robe Demon that Zhu Bajie and Sha Wujing cannot defeat, and Bajie is forced to apologize to Sun Wukong and invite him back to save Tang Sanzang.

Trivia

 * Despite appeared in only one occasion, Baigujing is one of the most popular Journey to the West villains, bar the Bull King and Princess Iron Fan.
 * It is heavily implied that Baigujing is possibly a human who transformed into a demon after death, which if is true, would make her unique among the Journey to the West demons, whose original self is either a magical animal or an ordinal animal (or occasionally a deity or at least a servant of deities), she was just a normal human.