Yun Xinyue (云心月) is a member of the Guardian Family, the Yun Family. Before Yun Che showed up Yun Xinyue was regarded as the strongest and most talented of the Yun Families Younger Generation; he had a Cyan Profound Handle, along with his father being the Seventh Elder Yun Waitian, who was the most likely candidate to become the Patriarch of the Yun Family, along with his good temperament was well liked by everyone.
During the Yun Family Competition his father tried pushing for Yun Qinghong to be abdicate his position as to become the Patriarch. But with the help of Hui Ye, Yun Xinyue was set to be the next patriarch until Yun Che exposed their scheme and used a Profound Handle Soul Search as proof to uncover the truth that he was responsible for attacking Yun Xiao and Number Seven Under Heaven, and he was working for someone from Duke Huai Palace.
He looked around twenty-five years old, and his expression was thriving with heroic spirit. 
Cunning, amazing actor, and good natured. (it is unknown what his true personality is as we have only seen him when his life was being threatened)
Six years ago he was poisoned by his master with the ‘Heart Disabling Venom’, and if he followed his instructions, and after his master overthrows the Little Demon Empress and he as the new Patriarch of the Yun Family, he would be named with the title of a king and if he where to disobey he would kill him. His master is from Duke Huai Palace’s.
Yun Xinyue is first seen right after Yun Xiao brings Yun Che into the Yun Family compund and says hello to Yun Xiao and introduces himself to Yun Che who later detects a faint killing intent comin from him, which leads Yun Che to speculate that it was him who attacked Yun Xiao and Number Seven Under Heaven. 
When the Yun Family Competition gets to the part where they are planning on chaing the Yun Family Patriarch, at first it was his father who was going to become the next patriarch but with the help of Duke Hui Ye Yun Xinyue was to be the next Patriarch. 
After the descision was made Yun Che made on objection and accused Yun Xinyue that he was the one that attacked Yun Xiao and Number Seven Under Heaven, while the proof would be revealed with a Profound Handle Soul Search, which Yun Xinyue refused to have that done to him as he would known the outcome. This eventually lead to Yun Qinghong speaking up and revealing that he had the Patriarch’s Crest  which had been lost for a hundred years, and when he still hesitated to be soul searched Yun Qinghon had one of the Grand Elders force a soul search onto him, revealing that he was responsible for the attack but was also poisoned with Heart Disabling Venom and forced into doing heinous crimes for his master.