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 then returned to the living world in the body of Mo Xuanyu, who had summoned Wei Wuxian's soul through a Sacrificial Ritual.
In his original body, Wei Wuxian was considered quite handsome, ranking fourth in the list of top cultivator gentlemen of his generation.  The tips of his eyes and eyebrows typically retained the hint of a grin, though he became noticeably colder and paler after his turn to Demonic Cultivation. 
In his youth, he wore the purple robes of the Yunmeng Jiang Sect. After turning to Demonic Cultivation, however, Wei Wuxian wore black robes. His flute Chenqing hung at his waist, adorned with blood-red tassels. 
Beneath his carefree attitude, however, Wei Wuxian cared deeply for those he loved. He possessed a self-sacrificing spirit that ranged from mild risks like sneaking alcohol to his friends in the Cloud Recesses, to being willing to have his own hand removed if it meant placating the Qishan Wen Sect's ire towards the Yunmeng Jiang Sect.  In fact, he went so far as to have 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 endured the entire operation awake and without pain medication for two nights and one day. 
Intelligent and inventive, Wei Wuxian openly inquired to Lan Qiren whether there was a way to utilize resentful energy instead of suppressing it.  Once he found himself thrown into the Burial Mounds without his golden core, he invented Demonic Cultivation and within three months was capable of massacring an entire supervisory office. 
Wei Wuxian had a strong sense of justice. For instance, he quickly joined the fight against Wen Chao in the cave of the Tortoise of Slaughter despite the risk.  He was bold in protecting the innocent no matter their name or societal prejudice.  As a result of his sense of justice, however, he was at times capable of ruthlessness: torturing Wen Chao to death for his role in the massacre of Lotus Pier,  using Demonic Cultivation to have members of the Qishan Wen Sect killed by the corpses of their own families and friends,  and, eventually, using the Stygian Tiger Seal to battle three thousand cultivators after the death of his sister Jiang Yanli. 
Nevertheless, Wei Wuxian was more than capable of expressing regret and admitting his faults. He believed that he became worse and worse every time he met Lan Wangji in his first life, and intended 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 cultivational society, Wei Wuxian saw nuance where many others did not. Despite the fact that Jin Guangyao had attempted to frame him for mass murder at the Second Siege of the Burial Mounds, Wei Wuxian expressed caution when further evidence of Jin Guangyao's misdeeds emerged. He considered that the actions of Nie Huaisang were not necessarily those of justice, noting that many of Jin Guangyao's apparent kindnesses were currently unexplained.  Moreover, even after learning Jin Guangyao's role in his first death, Wei Wuxian remained skeptical on many of the resulting rumors, as he recognized that similar untruths had once been spread about himself. 
- In his original body, Wei Wuxian ranked fourth on the list of best-looking young men in the cultivation world. 
- Wei Wuxian was 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.
- According to Baidu, his birthday is October 31 (Halloween in modern times).
- Wei Wuxian adored extremely spicy food. While Yunmeng cuisine was typically spicy, not even Jiang Cheng could tolerate Wei Wuxian's use of spice. 
- Wei Wuxian was a talented artist, capable of drawing a "vividly realistic" portrait of Lan Wangji. 
- His handwriting was notably messy.