Known as the Yiling Patriarch (夷陵老祖, Yílíng Lǎozǔ), Wei Wuxian died in the First Siege of the Burial Mounds thirteen years prior to the start of the Novel. He returns to the living world in the body of Mo Xuanyu, who summons Wei Wuxian's soul through a Sacrificial Ritual.
In his original body, Wei Wuxian is considered quite handsome, ranking fourth in the list of top cultivator gentlemen of his generation. The tips of his eyes and lips typically retain the hint of a smile, though he becomes noticeably colder and paler after his turn to Demonic Cultivation.
In his youth, Wei Wuxian wears the purple disciple robes of the Yunmeng Jiang Clan. After turning to Demonic Cultivation, he wears black robes. His flute Chenqing hangs at his waist, adorned with blood-red tassels.
Beneath his carefree attitude, Wei Wuxian cares deeply for those he loves. He possesses a self-sacrificing spirit that ranges from mild risks like sneaking alcohol to his friends in the Cloud Recesses, to being willing to have his dominant hand severed if it means placating the Qishan Wen Clan's ire towards the Yunmeng Jiang Clan. He has his own Golden Core transplanted into his sworn brother Jiang Cheng after Jiang Cheng's own core had been melted. During the transplant, Wei Wuxian endures, awake and without pain medication, for two nights and one day.
Intelligent and inventive, Wei Wuxian asks Lan Qiren whether there is a way to utilize resentful energy instead of suppressing it. Once he finds himself thrown into the Burial Mounds without his golden core, he invents Demonic Cultivation, and within three months is capable of massacring an entire supervisory office.
Wei Wuxian has a strong sense of justice. He quickly joins the fight against Wen Chao in the cave of the Xuanwu of Slaughter. He is bold in protecting the innocent no matter their name or societal prejudice. As a result of his sense of justice, he is capable of ruthlessness: torturing Wen Chao to death for his role in the massacre of Lotus Pier, using Demonic Cultivation to kill members of the Qishan Wen Clan with the corpses of their own families and friends, and, eventually, using the Yin Tiger Tally to battle three thousand cultivators after the death of his sister Jiang Yanli.
Nevertheless, Wei Wuxian often expresses regret and admits his faults. He believes that he became worse and worse every time he met Lan Wangji in his first life, and intends the words "thank you" to draw a clear distinction between himself and the noble Lan Wangji.
As a result of his experiences as both a hero and a pariah to the cultivation world, Wei Wuxian sees nuance where many do not. Despite Jin Guangyao attempt to frame him for mass murder at the Second Siege of the Burial Mounds, Wei Wuxian expresses caution when further stories of Jin Guangyao's misdeeds emerge. He states that the actions of Nie Huaisang are not necessarily justice, noting many of Jin Guangyao's apparent kindnesses. Even after learning Jin Guangyao's role in his first death, Wei Wuxian remains skeptical on many of the resulting rumors, as he recognizes that similar falsehoods had once been spread about him.
- Wei Wuxian is severely cynophobic due to the trauma of fighting stray dogs for food while living on the streets as a child.
- Mo Xiang Tong Xiu referred to Wei Wuxian in her author's notes as Wi-Fi. This is because Wi-Fi = 无线 (wuxian) is a homophone of his courtesy name.
- His birthday is October 31, as Mo Xiang Tong Xiu decided to assign the birthdays of all her protagonists as the day the first chapter of their novels were posted. Coincidentally, this day is Halloween in modern times.
- Wei Wuxian adores extremely spicy food. While Yunmeng cuisine is typically spicy, not even Jiang Cheng could tolerate Wei Wuxian's use of spice.
- Wei Wuxian is a talented artist, capable of drawing a "vividly realistic" portrait of Lan Wangji.
- His handwriting is notably messy.
- Before his infamy, he was said to be a master of the six arts: rites, music, archery, charioteering, literacy, and numeracy.
- On Weibo, Mo Xiang Tong Xiu once wrote a snippet of Wangxian's interactions in a modern alternate universe. Wei Wuxian is the type of student who obtains good grades, but ignores school uniforms and makes a mess of the laboratory. This earns him the attention of Lan Wangji, his classmate in charge of discipline, and Lan Wangji deducts many points from Wei Wuxian.
- Mo Xiang Tong Xiu's Weibo also details that while Wei Wuxian lived on the streets of Yiling, he was not rambunctious nor talkative. He was a nice-looking but dirty kid with disheveled hair, who tended to stare at people and spent his time picking up the rinds that others did not want to eat. If someone gave him a leftover bun, he would laugh and display a very happy smile.
- After Wei Wuxian arrived in Lotus Pier, he spent the first month afraid to eat more portions or use too much bathwater, because he worried that Jiang Fengmian would decide he was too expensive to raise."