Lady Hyacia

A powerful demon that wields the Soul-Scattering Hammer. Her actual essence is not physical, so she must possess several bodies to be able to use her powers fully. Currently, she inhabits the body of Sorceress Renshou, and Renshou's consciousness is present within her, and is even a part of her. Powerful as she is, she has little defense against techniques that cause her soul to leave her body. Hyacia was born from the dark emotions: Hatred, Bitterness, Pride, Malice, and Cruelty that were left over when Ban-Go was murdered. According to Laobi and Louen, she is the Heavenly Tiger who is attendant to the Empress Mother of the West. Hyacia is quite taken with Rey Yan and does all in her power to help the young man. However, when speaking with Ban-Go about Rey, Hyacia states that she prepared Rey's body, and that of another, to be able to withstand the power of Ban-Go. She even says "I will give Rey everything I have... until his final moment." Hyacia rules over the demons of the human realm in the place of the Heavenly Realm, and gives the Sorcerers of Human Realm their power. Her control has created much resentment amongst the Demons of the Human Realm. Hyacia has an uneasy past with Sword Sage Shouren. Despite her connections with the Heavenly Realm, Hyacia has some distaste for the Sages that watch over the human realm. She also seems to oppose Prime Minister Shiyan 's plans for Rey. What her ultimate goal is has yet to be revealed, but it known that has something to do with the death of the Heavenly Gods and the Demon Emperor.

By the end of the series (volume 37), she is hinted to have been proposed by Rey to live together after Rey defeated Shiyan.

Background
Her identity is unconfirmed, though she is definitely a being of immense power. Her initial form disintegrated a long time ago, and so now she lives in another host. Her strength is almost without equal in the demonic and heavenly realms, but because she doesn't a physical body of her own, she is weak against certain techniques that make her soul leave the body she's in ( Shouren fights with techniques like this, as you see in volume 8). Her soul is not much affected by these attacks, but such techniques force her to look for another host. At the moment, she is weary of her long life and her references to "darkness", "filth", "chaos" and "hate" hint at a darker side to her personality. And what exactly is the nature of her feelings for Rey...?

She appears cheerful on the outside but her inner thoughts remain a mystery. She keeps to herself, but does show some tenderness toward Rey. Hyacia is also the favorite female character among the fans.