At the very beginning of time, shortly after Pan Gu separated Heaven and Earth, four spiritual beasts were formed from the mystical essences: Baixi, Tengshe, Qilin, and Baize.
Nuwa, an all-powerful half-human, half-demon creature who was given the responsibility of fashioning mankind from clay, took the four of them in as her disciples, and they learned the arts of magic and immortality under her. Baixi and Tengshe, in particular, were regarded as having a relationship as intimate as that of biological sisters. Unfortunately, this was only partly true: Tengshe, as the most temperamental and stubborn of the spiritual beasts, secretly harboured a jealousy of her senior as she felt that Nuwa was always inclined to favour Baixi over her, to the extent where she reserved the teachings of the deepest secrets of her magic only for Baixi (in her own opinion). Baixi, on her part, later confessed that her behaviour might have occasionally been dictatorial and insensitive with regards to Tengshe's feelings, but her sisterly love for Tengshe was genuine, and she actually blamed herself for her junior's falling from grace.
When the universe was endangered by the phoenix (one of the four mythical beasts) and his minions, the four spiritual beasts responded to the pleas of help from Nuwa, and helped to fight against the forces of evil. Baixi and Tengshe emerged as two of the few victorious survivors of this colossal battle, which was said to have lasted forty-nine days. For saving the universe from utter destruction, Nuwa was personally welcomed into the divine realms by the Heavenly Emperor himself, and honoured as the First Primordial Great Goddess, with a rank far beyond all other divinities. Baixi and Tengshe also made high-ranking Goddesses in their own rights, becoming the left and right-hand woman of Nuwa respectively, and escorted their mistress into her new residence: the Palace of the Ninth Heaven.
Later on, she was sent down to the human realm by her mentor, Goddess Nuwa, to defeat the underworld lord, Shi You Ming, who was creating havoc on the human realm at that time. But being the last mythical creature of his kind, she allowed him to live, out of the kindness of her heart. In return, he was never to return to the human realm. After some time, the fighting of humans against each other angered Tian Di, thus ordering Xian Yue to return to the Heaven Realms, before recleansing the humans. As she disagree with Tian Di, she ignored the order and stayed back with her junior, Mo Yin, to protect the human realm from Tian Di's punishment with the help of the King of the Dragons, Cang Long. But by doing so caused consequences to her. She was not allowed to return to the Heaven Realms. The humans were grateful to her for saving their lives, thus proposing her to become the Grand Priestess of Nan Yue. Xian Yue was willing to give up her Godhood to stay back in the human realm, and became the first Grand Priestess of Nan Yue.
Despite the promise she made to her mentor, Xian Yue fell in love with Wen Tian, who was a human-dragon hybrid. They met 20 years prior to the series when Wen Tian tried to steal the Demon-Subduing Vase which resided in Nan Yue's forbidden area, the ancient tomb, where Xian Yue was coincidentally residing at the same time. Xian Yue chased him for 3 days and 3 nights. Somehow, they fell in love and vowed to spend their lives together, hidden from the world. However, both were tricked by Shi You Ming, a demon infatuated with Xian Yue; Xian Yue died due to her fatal wound and overuse of her power while Wen Tian was sealed and imprisoned in the ancient tomb. 20 years later, Xian Yue was brought back to life by an underworld witch, using her reincarnation, Ding Yao's soul. In return, the witch hopes to use her to conquer the underworld. However, Xian Yue killed the witch before she had the chance. As Ding Yao took back her soul, Xian Yue became a walking body with no soul. She had to rely on a mythical creature's blood, found in Nan Yue only, to survive. While she was alive, she discovered that there was a mole in the palace. She was determined to find who it was and the truth of what happened between her and Wen Tian. Xian Yue's final death is due to fatal wounds occurred during the battle with Shi You Ming and her junior Mo Yin, who joined forces to kill her.
Her sole purpose for staying alive is to kill Shi You Ming before he could rebuild and use the Demon-Subduing Vase to take over all three realms. She tried various times to kill him, but was unsuccessful.
Xian Yue is an extremely beautiful woman with a clear flawless complexion, a wealth of thick black hair that flowed almost to her waist, and a petite yet well-built figure. She was always dressed in long, flowing, embroidered white robes, her hair was set with an exquisite elaborate headpiece of pink diamonds and gold, and matching jewels hung from her ears. She was often seen with her arms folded, carrying the flute through which she works her strongest magic into reality.