|General of Lü Bu|
When Lü Bu wandered the land, Wei closely followed him in the journey, together, they routed the Heishan Bandits, and fended off attacks from Yuan Shu. Besides being an adept rider, Wei was also a relative of Lü Bu, so he was heavily trusted by the latter, once, Lü even granted Wei the control of Gao Shun's crack troops. However, in 198, when Cao Cao besieged Lü during the Battle of Xiapi, Wei Xu and his colleagues, Hou Cheng and Song Xian, kidnapped Lü's chief advisor, Chen Gong, and defected to Cao's side. Lü was soon captured and executed, along with Chen and Gao.
In chapter 19 of Luo Guanzhong's historical novel Romance of the Three Kingdoms, Wei Xu's close friend and colleague Hou Cheng was flogged 50 times on Lü Bu's order for breaking a liquor ban. The disgruntled Hou then plotted with Song Xian and Wei Xu to betray Lü Bu to Cao Cao.
Under the cover of the night, Hou stole Lü Bu's steed Red Hare and galloped out of the city towards Cao Cao's camp. The next morning, Cao Cao's troops launched a fierce attack. Lü had to personally take part in the defense of the walls. The battle dragged into high noon when at last the offensive subsided. The exhausted Lü then took a nap on top of the city gate. Taking the opportunity, Song Xian and Wei Xu tied Lü up and hoisted a white flag. The pair also threw Lü's halberd down the wall as proof of allegiance. Seeing the signals, Cao Cao's troops then flocked into the city and seized it in no time.