Reserved, taciturn and unbendingly upright, Lan Wangji follows the thousands of rules of the Cloud Recesses to the letter. Behind this impassive mask lies absolute devotion, expressed in deeds rather than words, and a cold anger at injustice.

An elite cultivator, he wields the sword Bichen and the guqin Wangji, which he uses to fight and to calm spirits. He masters "Inquiry", a song that lets him question the souls of the dead, one of the keys to the investigation.

A model student of the Cloud Recesses, he meets Wei Wuxian when the latter comes to study there, and their rivalry slowly becomes a deep bond. During the war against the Wen clan, and then at Wei Wuxian's downfall, he is one of the few to defend him, which earns him a harsh punishment from his sect. He spends the next thirteen years hunting spirits while hoping for his return.

Wei Wuxian is the centre of his life, and he is the only one to recognise him beneath his new face. He deeply respects his elder brother, Lan Xichen, and his uncle Lan Qiren, keeper of the rules. He also watches over the young disciples, including Lan Sizhui.

In the donghua he is voiced in Chinese by Bian Jiang. In the drama The Untamed he is played by Wang Yibo. Censorship forces the adaptations to suggest his love for Wei Wuxian, which the novel fully embraces.