Chui-Bi

Chui-Bi was the concubine of the previous king of Myung-Joo and the biological mother of Mu-Hyang.

Overview
Chui-Bi once loved the previous king of Myung-Joo. At first she was glad just to be near him, even if meant just being his concubine. However when he married another woman who offered no political advantages, she became angry and hateful towards him, who never looked her as a woman and refuse to sleep with her, or as she puts it, visits her quarter. Chui-Bi later had a son, Mu-Hyang. Though many believed Mu-Huang was the king's illegitimate son as the king never openly denied it, Mu-Huang was the son of a another man entirely.

When his queen had a child, Chui-Bi's hopes to become queen and for her son to someday take over Myung-Joo was crushed. Chui-Bi's flashback reveals that she played a part in the death of the previous king of Myung-Joo. Furthermore, No-Woo reveals that Chui-Bi has attempted multiple times to arrange the assassination Hong-Ryung, the current king of Myung-Joo, so that her son can become king of Myung-Joo instead. However, Hong-Ryung spared her life because Mu-Hyang begged him not to punish his mother.

Personality
In the series, Chui-Bi is presented as cold and cruel, and deceitful as she hides behind a smile while hating Hong-Ryung, and wishing for his death so that her son can become king of Myung-Joo.