Lan Zhan (蓝湛 Lán Zhàn), courtesy name Lan Wangji (蓝忘机, Lán Wàngjī) is the second young master of the Lan clan. Titled as Hanguang-Jun (含光君, Hánguāng-jūn), Lan Wangji is one of the Two Jades of Lan alongside his older brother, Lan Xichen. After thirteen years of mourning, he recognised Wei Wuxian in the body of Mo Xuanyu and helped to clear Wei Wuxian's name. He later becomes cultivation partners with Wei Wuxian.
Lan Wangji made his reputation spread in the Sunshot Campaign against the Qishan Wen Sect. Following this and the first siege of the Burial Mounds, the next thirteen years would see Lan Wangji become known for 'being where the chaos is'. It is mentioned that during the thirteen years between Wei Wuxian's death and his reincarnation in Mo Xuanyu's body, he is described as looking as if he had lost his wife, due to his intense feelings of love towards Wei Wuxian.
From his youth the marks of a strong conscience and good upbringing could be spotted. He was described by Wei Wuxian as being someone courtly and righteous and well versed in etiquette, unwilling to bend the rules even if he would be dragged down in punishment. In his youth this was tempered by some innocence - he accepted at face value Wei Wuxian's claim that freshly picked lotus seeds would taste better, for one, and was also tricked into picking up a pornographic book by the same person. He always displayed an air of elegance and a face of indifference, which is revealed to be due to his harsh circumstances, including his mother's death, his father's illness, and having been separated from his brother while the Cloud Recesses were burning. Wei Wuxian hypothesizes that these are the reasons Lan Wangji grew up to be cold and distant from others.
As he grew up and became more familiar with Wei Wuxian, more and more facets of Lan Wangji become apparent - for one, he tended to be standoffish first but later becomes more and more deeply involved in Wei Wuxian's safety. He is deeply jealous of Wei Wuxian's random flirting with women, and he keeps rabbits. While the exact time when he fell in love with Wei Wuxian is unknown, it is evident that his feelings for him are quite strong. When Wei Wuxian became the Yiling Patriach and kept his distance from Lan Wangji, Lan Wangji did everything in his power to help Wei Wuxian and tried to stop his corruption. He even went against his uncle and injured thirty three elders to protect Wei Wuxian. After Wei Wuxian died, his personality changed. He began to go through the same experiences Wei Wuxian had such as drinking wine and raising rabbits and played inquiry to find his spirit. Despite remaining outwardly aloof and elegant, he demonstrated much greater tolerance for Wei Wuxian's antics and even managed to make a snarky comment back at him mirroring a similar comment Wei Wuxian made in the past. According to Wei Wuxian, he disliked being touched but was shown to be fine with Wei Wuxian touching him later on (though this could be due to his feelings for him). He is shown to have a temper, often getting angered by Wei Wuxian's antics in the past and also being deeply jealous and annoyed when Wei Wuxian gets close to others. He also has a deep sense of honor and justice and cannot stand wrongdoing and evil. In fact, unlike most cultivators who refuse to handle minor demons and spiritual problems under the claim that it would be too much work, Lan Wangji would always help anyone in need no matter how small or how little fame would be acquired from the act. It can be inferred that he is stubborn and also protective of those he cares for, as evident by his relationship with his brother, his mother, and Wei Wuxian. When his mother died, he continued to go to her house (as she was placed under house arrest apart from her family) long after her death despite knowing she would never come back. He similarly played Inquiry for thirteen years to find Wei Wuxian's soul.
When drunk, Lan Wangji becomes incredibly childish, even playing a game of Hide-and-seek with Wei Wuxian. Because of his extremely low tolerance to alcohol, Lan Wangji becomes honest, incapable of lying, to the point of answering all of Wei Wuxian's questions without hesitation. Wen Ning also tends to become the target of his ire - being the next closest being to Wei Wuxian.
- Lan Wangji ranks second on the list of cultivator gentlemen of his generation.
- His fan nickname is Wangji (汪叽), a homophone of his courtesy name.
- On this note, fans also call him "Second Brother Lan" (蓝二哥哥). This is the second of a trend where the semes in Mo Xiang Tong Xiu's works are counted in the order of appearance (Big Brother Luo, Second Brother Lan, Sanlang (third son), etc).
- His (lack of) ability to drink is genetic.
- The phrase "playing Inquiry for thirteen years, waiting for the unreturning one" summarises Lan Wangji's state before the novel's opening.
- He apparently likes to tie up Wei Wuxian during sex.
- Although he possess a mild taste, Lan Wangji often tastes spicy dishes to satisfy Wei Wuxian's love for (extremely) spicy food.
- Lan Wangji's love for rabbits originates from Wei Wuxian himself, when he brought two rabbits to Lan Wangji when they were younger. Wangji is revealed to be raising quite the number of rabbits in the Cloud Recesses.