Jiang Cheng (江澄 Jiāng Chéng), courtesy name Jiang Wanyin (江晚吟 Jiāng Wǎnyín), is the current leader of the Yunmeng Jiang Sect and the uncle of Jin Ling. He is also known by his title, Sandu Shengshou (三毒圣手 Sāndú shèngshǒu).
In his younger years, Jiang Cheng was strict but caring. He was straight laced and often annoyed by Wei Wuxian, but loved him like a brother and got along well with him. He had a short temper but knew to respect his elders and superiors and often warned Wei Wuxian that his antics would get him into trouble. He showed deep care for his friends and family, becoming angered by negative comments about Wei wuxian and his sister Jiang Yanli. Wei Wuxian notes that he has always had a bad temper and if pushed, he will say anything negative to hurt the other person regardless of the consequences. Despite this, he knew who to be cautious of as he tried to prevent Wei Wuxian from getting into fights with Jin Zixuan as he was to be his brother in law.
He has been competitive since young and refuses to lose or be defeated by anyone in anything regardless of how trivial the matter. He possessed a deep inferiority complex which continued even as he grew older, and pushed high expectations on his clan and his nephew, once even telling him he did not wish to speak to him unless he captured the spirit beast on Dafan Mountain (which turned out to be a smiling goddess). He had an inferiority complex to Wei Wuxian as he felt his father loved him more than him and because in terms of capability and on list of cultivator gentlemen he ranked just below Wei Wuxian, but Wei Wuxian assured him that he would be a loyal servant and equal to Jiang Cheng when he grew up, easing their relationship. After his parents and many of his sect's disiciples were murdered by the Wen Clan, he grew to despise them with his heart and did everything to get revenge against them. His hatred was such that when Wei Wuxian saved two Wen clan members (Wen Ning and Wen Qing) it caused a great strain in their relationship. It has even been mentioned that he no longer knew how to love. His feelings for Wei Wuxian turned into pure hatred once Wen Ning (who became Wei Wuxian's walking corpse and servant) murdered Jiang Yanli.
Jiang Cheng then became a man conflicted by vengeance and anger, as he despises Wei Wuxian for inadvertently orphaning Jin Ling and seeks to find his spirit to question and punish him. The mention of Wen Ning equally sends him into a rage. His strict nature is well known to be frightening, as his nephew Jin Ling often avoids him when he knows he is angry. Despite this, he still retains love for Jin Ling, his nephew and only blood relative and acts in a similarly stringent manner towards him as his own mother did to him as a child. His anger is well known as the mention of his name is enough to scare most people. He is not popular in Yunmeng city, which is under his district due to his horrific temper and anger issues and is even blacklisted by female cultivators list of potential husbands as a result. He is a man fueled by vengeance and despises anyone who uses the dark arts, as it reminds him of Wei Wuxian. He will even kidnap and torture people he suspects of using dark arts or of possessing Wei wuxian's soul whether they are innocent or not. Jiang Cheng's two consistent traits are his love for his family and his ability to hold deep grudges though by the end of the book he relinquishes his hatred towards Wei Wuxian after finding out the truth about his golden core.
Another negative quality of his would be his desire to prove himself and the importance he places on status and reputation. When he was younger he refused to recognize Jin Guangyao's deeds despite how great they were, stating that because he was the son of a prostitute he could never be anything more despite Wei Wuxian's praise for him. Similarly, he had a superiority complex where he desired to be better than anyone at any competition which is what fueled his one sided rivalry with Wei Wuxian whom he understood would always surpass him in cultivation which is what strained their relationship to an extent. In addition, after the murder of his sister and brother in law by Wei Wuxian (by accident through the orchestration of Jin Guangyao) it was easy for the other sects (who took advantage of the strain in their relationship) to convince Jiang Cheng to betray his own adoptive brother and kill Wei Wuxian by leading the Nightless Siege. Similarly, while he was placated when Wei Wuxian promised to be his servant and protect him, he was angered at the fact he broke that promise. While the two were close as brothers, the fact that Jiang Cheng wished for Wei Wuxian to be his servant rather than as a sworn brother (along with his mother's own anger that Wei Wuxian, a servant's son, managed to outclass Jiang Cheng, the heir to one of the biggest cultivation clans, who couldn't surpass him) suggests that he wanted Wei Wuxian as a servant to remain dominant in their relationship and signifies his inability to recognize or accept someone superior to him especially if they were of lower social status.
- Jiang Cheng ranks fifth on the list of young gentlemen in the cultivation world.
- Jiang Cheng went on to 3 blind dates. For various reasons, he got blacklisted by all the female cultivators.
- Jiang Cheng's requirements in his partner are: naturally beautiful, graceful and obedient, hard-working and thrifty, coming from a respected family, cultivation level not too high, personality not too strong, not too talkative, voice not too loud and must treat Jin Ling nicely.
- When he was a child, Jiang Cheng used to have puppies whom he called with corny names such as "Jasmine", "Princess", and "Little Love". However, after Wei Wuxian was brought to live at Lotus Pier, he was forced to send away the puppies because Wei Wuxian was scared of dogs. This caused Jiang Cheng to take an initially unpleasant atittude towards Wei Wuxian for some time.
- Jiang Cheng inherited both of his facial features as well as his personality from his mother, Madam Yu. He is known, therefore, to be short-tempered and harsh, same as his mother.