The Founder of Diabolism

After Lan Wangji successfully stops the mysterious arm, Wei Wuxian escapes to prevent being spotted by him. He arrives at the nearby Mt. Dafan and meets another young disciple, Jin Ling from the Jin sect. The two have a heated argument which causes Jiang Cheng to come by. Wei Wuxian then learns that Jin Ling is the nephew of Jiang Cheng, whom was left orphaned because of Wei Wuxian's past mistakes. Due to being in Mo Xuanyu's body, Jiang Cheng was unable to recognise Wei Wuxian until the latter starts using his demonic abilities to save everyone from the escaped arm, which summons the Ghost General Wen Ning. While he suspects Wei Wuxian, the latter plays dumb and acts as the notorious cut-sleeve Mo Xuanyu to prevent his cover from being blown. As Lan Wangji also has the same suspicion, he protects Wei Wuxian and even offers to take him back to Gusu when Wei Wuxian speaks of his liking for him, catching Wei Wuxian by surprise. At the end of the episode, the timeline changes to twenty years ago, starting the flashbacks of Wei Wuxian's teenage years.

Wei Wuxian, Jiang Cheng, and their friend Nie Huaisang, start their education in the prestigious Cloud Recesses to become better cultivators. They meet the top disciple Lan Wangji, whom Wei Wuxian confessed he had angered upon his arrival in Gusu. Due to Wei Wuxian's playfulness, he broke three rules during his first encounter with Lan WangJi, and thus is resented by both the latter and the teacher Lan Qiren. However, despite his mischief, he is shown to be a knowledgeable student, although his solutions involve the use of the forbidden demonic path. He is then punished to copy passages in the Library Pavilion and to be supervised by Lan Wangji, much to Wei Wuxian's dismay as he does not chat with him. One month later, Wei Wuxian finishes the punishment and draws a portrait of Lan Wangji as a farewell gift. But this is just another of his pranks as Lan Wangji was drawn femininely. Wei Wuxian also replaces Lan Wangji's poetry book with an erotic art book, causing a fight to break out in the library as Wei Wuxian teases him continuously.

The disciples of the Cloud Recesses are brought along to Biling Lake to exorcise the water ghouls that had mysteriously appeared recently. While they pass by Caiyi Town, they discover that water ghouls had also arrived in town. The disciples are puzzled as the corpses were not recognised by the locals and appear in a place where they did not drown in. As Biling Lake is overflowing with resentful energy, Wei Wuxian comes up with the idea to harvest these energy to counterattack the water ghouls, causing Jiang Cheng to stop him using the threat of copying more passages. Subsequently, Wei Wuxian discovers a water ghoul hiding below Lan Wangji's boat, causing Lan Xichen to be impressed by his wits. The Waterborne Abyss then starts attacking, causing some boats to capsize. While Wei Wuxian is saving one of the disciples, he is dragged into the water and met with resentful energy up-close for the first time. Thankfully, he is pulled out of the water by Lan Wangji before anything can happen. With the problem at hand finally solved, the disciples start to suspect the Wen sect's malicious intent

Wei Wuxian sneaks out at night again to enjoy his favourite wine, but is caught by Lan Wangji for the second time. As Wei Wuxian does not want to give up, he fights with him and causes them both to fall outside of the Cloud Recesses, which is a rule broken. This causes them to be punished by being beaten. After hearing of a way to relieve the pain, Wei Wuxian joins Lan Wangji in the Cold Spring. Wei Wuxian uses this as an attempt to make friends with him, but Lan Wangji continues to refuse. Later, they hear a strange sound and rushes to defeat the feral zombies that have escaped. Lan Wangji holds up until Jiang Cheng and another disciple comes to give Lan Wangji his guqin, and successfully defeats the zombies. On the other hand, Wei Wuxian does not have a weapon and faces difficulties at his end. While fighting, he sees a rabbit and protects it while running from the zombies. One of them gets too close and resentful energy starts entering his body. Jiang Cheng comes just in time to return him his sword and they defeat the remaining zombies. Jiang Cheng then gets mad Wei Wuxian attempted to harness the resentful energy, which is forbidden and warrents his execution, but Wei promises not to do so again, having resisted its influence.

While the disciples learn about Lan sect's history, the topic of love raises a question towards Jin Zixuan about which lady he thinks is the fairest. Wei Wuxian comments that Jin Zixuan will choose his fiancee Jiang Yanli, but Jin Zixuan badmouths her. As her brothers, both Wei Wuxian and Jiang Cheng gets offended and Wei Wuxian starts a fight with him. The fight causes their father Jiang Fengmian to personally come to Cloud Recesses to bring Wei Wuxian home. Back at Yunmeng, Wei Wuxian is finally reunited with his adoptive family, but his mother Yu Ziyuan despises him, mostly due to Jiang Fengmian's favouritism over an adopted son. The situation gets worse when the marriage is called off and Yu Ziyuan blames it on Wei Wuxian, despite Jiang Fengmian's reasoning. Yu Ziyuan subsequently argues with Jiang Fengmian, straining their relationship further. Wei Wuxian overhears the argument and blames himself for the disputes between the two pairs. He apologises to Jiang Yanli but she insists that love should not be forced if not mutual. One year later, Jiang Cheng returns to Yunmeng after finishing his studies. As the brothers talk, Jiang Chen tells him an archery tournament between the cultivation clans will be held in the Nightless City - the home of the Wen Sect.

Wei Wuxian gets lost finding the archery field in the Nightless City and meets Wen Ning while he was practicing his archery. Wei Wuxian asks him for directions and makes an acquaintance. At the field, every capable archers and the respective sect leaders gather for the Grand Discussion that is hosted by the Wen sect this year. When Wei Wuxian spotted Lan Wangji, he pulls a prank on him into thinking his headband is slanted, making the latter annoyed. The clan leaders take their seats, the leader of the Wen Clan sitting higher then the leaders of the other clans in an obvious power play. Right before the competition starts, Wen Ning is picked on by Wen Chao, the Wen Clan's heir, in which Wei Wuxian steps in to defend his archery skills. However, when told to prove his skills, Wen Ning fails to make a good shot due to nerves. But Wei Wuxian continues to praise him, which leads to Wen Ning's great trust in him. During the competition, Wen Chao breaks his own rules and causes an argument to break out. When a disciple badmouths him, Wen Chao attacks him with no mercy. Lan Wangji appears in time and saves him, making Wen Chao leave in embarrassment. Wei Wuxian notices that Lan Wangji's headband is indeed slanted this time, but Lan Wangji refuses to believe. Out of kindness, Wei Wuxian tries to straighten it for him, but pulls the entire band off instead.

Wen Chao reports back to the Wen sect leader Wen Ruohan about the incident at the archery competition, stating that the four clans had tricked him. This leads to the start of a series of malicious plans to take control over the four clans. The Cloud Recesses is burned down by Wen Xu, leaving the Lan sect leader gravely injured and Lan Xichen to disappear without a trace. The Wen sect also orders for disciples to be dispatched to Qishan as an attempt to keep them hostage. Their swords are confiscated and they are forced to search for the cave that Wen Chao wants to night-hunt in. Anyone who disobeys will have their Golden Core melted by Core-melting Hand Wen Zhuliu. When Wei Wuxian learns of the burning of the Cloud Recesses, he offers to carry Lan Wangji on his back as his leg is injured. The latter once again refuses. During the search, Wei Wuxian saves Mianmian who is being harassed by Wen Chao, stalling him so his lover Wang Lingjiao can see his actions. In the cave, Mianmian is offered as a sacrifice to lure the beast out, but some disciples disobey and protected her instead, causing Wen Chao to order his people to kill them. The commotion from the resulting fight causes the beast to wake. Wang Lingjiao attempts to brand Mianmian's face with her branding iron despite the chaos but Wei Wuxian gets in the way, being branded on the chest.

With the beast angered, the Wen sect escapes and block the cave entrance, preventing anyone else from leaving. Lan Wangji points out there is another opening as there are maple leaves in the pond despite the lack of trees, meaning there's a tunnel connected to the outside in the pond. As the beast returns to sleep, Wei Wuxian and Jiang Cheng dive into the water to search for the way out. However, Wei Wuxian accidentally awakens the beast when a body surprises him, but Jiang Cheng emerges with good news. Wei Wuxian stays to hold off the beast with a flame array while the others escape. Su She, while attempting to shoot the creature, accidentally shoots him in the shoulder with an arrow, causing Wei Wuxian's powers to weaken faster. The scent of blood incites the beast, which he uses to distract it so Jiang Cheng can help the last few escape. Lan Wangji saves Wei Wuxian, the beast biting his leg, but the two hide from it. However, its thrashing has caused the tunnel to the outside to collapse and those who escaped are attacked by Wen trying to kill them. They tend to each other's wounds and Lan Wangji tearfully confesses about his worry for his family. They decide to wait for three days to regain their strength before attempting to fight the Tortoise of Carnage by themselves. They attempt to fight the beast with the Lan sect's Killer String Technique. When Wei Wuxian dives in to lure the beast, he is drawn to a mysterious sword deep within full of resentful energy. He struggles to control the resentful energy and is swallowed by the monster. Working with Lan Wnagji outside, the kill the beast. However, an unconscious Wei Wuxian sinks through the water, the sword vanishing in the depths of the pond.

Lan Wangji pulls Wei Wuxian out of the water. In an attempt to keep him awake, Lan Wangji plays a song he has composed specially for him, although the latter passes out anyway. Wei Wuxian wakes up in his own room after being saved by Jiang Cheng. He then learns the Lan sect leader has passed away and the Wen sect has taken all the credit for killing the beast. When Jiang Fengmian and Yu Ziyuan comes to visit, the family once again has an argument over Jiang Fengmian's unfair treatment to Jiang Cheng. When the parents leave, Jiang Cheng gets angry at his own father for never taking him seriously as a Jiang and recounts how he came back to Yunmeng with great difficulty. Wei Wuxian promises him he is worthy to be the next clan leader and he will be his subordinate, just like their own fathers, easing the tensions between the two. The Wen sect continues with their plan to set Supervisory Offices in every clans. Wang Lingjiao comes to Yunmeng to demand Yu Ziyuan to punish Wei Wuxian with Zidian. Without Jiang Fengmian around, Jiang Cheng is unable to stop her. Wei WuXian silently takes a whipping, hoping the Wen will then be satisfied and leave the Jiang alone. Wang Lingjiao afterwards tells Madame Yu to cut off one of Wei Wuxian's hands, which she seems to agree to until Wang Lingjiao tells her she will head the Supervision Office at the Lotus Pier and be given authority over Madame Yu. Then Madame Yu strikes her for not knowing her place.

The Wen sect start to attack the Lotus Pier and its shield formation. The barrier is brought down when Wen Zhuliu kills the Jiang maintaining it and the Wen unleash a barrage of flame arrows that set fire to the Lotus Pier before invading. Yu Ziyuan leads her sons into battle. However, the fight is too huge to handle and Madame Yu decides to put Wei Wuxian and Jiang Cheng on a boat to safety. She and Jiang Cheng share a tearful goodbye and Yu Ziyuan hands over Zidian to Jiang Cheng. Wei Wuxian is made to promise he will protect Jiang Cheng with his life and the two leave against their will, paralyzed by Zidian and taken away by the currents. They spot Jiang Fengmian on his way back to Yunmeng and Jiang Cheng fears for his safety. By the time they manage to return the place is in ruins. Over 1500 disciplines and cultivators of the sect are dead. When they see their parents dead near Wen Chao, Jiang Cheng acts on impulse and catches the attention of Wen Zhuliu.

Back in the Cloud Recesses, Lan Wangji is reprimanded for sending disciples to search for Wei Wuxian and Jiang Cheng as it is too dangerous, but Lan Qiren defends his motives. Lan Wangji laments the two are yet to be found, even though Jiang Yanli was safe. Wei Wuxian and Jiang Cheng take cover in a village, but the former finds Jiang Cheng missing when he returned with food. He rushes back to the Lotus Pier to save a weakened Jiang Cheng and Wen Ning hides them in his room to prevent them from being caught. While Wen Ning's sister Wen Qing originally disapproved, she eventually agrees to heal the brothers and keeps them safely hidden for a few days before Wen Chao returns. When Jiang Cheng wakes up, he reveals his golden core has already been melted and his spiritual energy is gone. To make matters worse, his instability causes him to get defensive against Wen Ning as he is of the Wen sect. Wen Qing then makes him sleep and tells Wei Wuxian to wake him up when he has recovered. Wei WuXian is quickly healed but Wen Qing says the only reason he recovered so fast is that Madame Yu didn't put her full force into whipping him. Wei Wuxian looks at his spiritual energy as he decides to help Jiang Cheng get back his golden core.

Wei Wuxian brings Jiang Cheng to Yiling to meet Baoshan Sanren, ordering him to keep his blindfold on at all times and introduce himself as the son of Cangse Sanren. As Wei Wuxian waits on the foot of the mountain, he is ambushed by the Wen sect and stabbed through the chest by Wen Chao's sword. Wei Wuxian dares him to brutally kill him because after he dies he'll turn into a vicious ghost and torment the Wen to no end. The Wen throw him into the Burial Mounds where no one, dead or alive, ever returns, and leaves him to die. Following a tip the Jiang brothers were seen at Yiling, Lan Wangji arrive but finds only Wei Wuxian's fallen bell. When he returns to Gusu, he plays Inquiry but there is no information on him, dead or alive. Lan Xichen returns, having recruited many of the smaller clans to join together and fight the Wen sect and found Jiang Cheng. The Lan sect holds a meeting in the Cloud Recesses to convince the major sect leaders to join their alliance. Jiang Cheng shows up to express his urge for revenge. He and Lan Xichen convince the others into joining them to fight. Back in the Burial Mounds, Wei Wuxian survives the fall and gives in to the resentful energy so he has the power to get revenge.

The Sunshot Campaign starts with the four clans marching into Qishan, but their attacks were in vain as Wen Ruohan overpowers them. Lan Wangji helps the Jiang sect by reinforcing their turf and Nie Mingjue beheads Wen Xu with his own hands. This victory boosts the morale of Nie Mingjue's followers and Wen Ruohan orders every branch of the Wen sect to join the fight. When the Lan and Jiang sects go to infiltrate the Wen sect one night, they discover that something else has already attacked the base, which has left most of its cultivators scared to death. Lan Wangji continues to find more places in the same situation. He affirms that the talismans have a reverse effect to summon evil and are drawn by the same person. On the other hand, Wang Lingjiao is panic-stricken as she suspects that Wei Wuxian has returned to haunt her and the clan. She eventually falls to the same fate as the talismans are altered. The Wen have also located the hideout of Jiang sect rebels and start an attack that overpowers them. Lan Wangji and Jiang Cheng are captured and Wen Chao reveals he killed Wei Wuxian in the Burial Mound months ago. However, a flute starts to play and a mysterious demonic cultivator arrives and reanimates the dead Wen...

The fierce corpses only attack the Wen sect. Lan Wangji calls the technique sinister but deems the demonic cultivator a friend. The deceased Wang Lingjiao starts to attack Wen Chao and Wen ZhuLiu, and the cultivator shows himself. The cultivator overpowers Wen Zhuliu and uses use resentful energy to tear out his golden core, which he smashes. He finally reveals himself to be Wei Wuxian, catching the three by surprise. Wei Wuxian continues using his dark abilities to kill Wen Chao and Wen Zhuliu. With both dead, Lan Wangji warns Wei Wuxian of the price of pursuing demonic cultivation and fears he will not be able to control it. Wei Wuxian has lost his past cheerful self and cannot detect Lan Wangji's act of kindness when the latter offers to take him back to Gusu so he won't have to keep using the techniques. Lan Wangji leaves the battlefield in anguish as Wei Wuxian stays with Jiang Cheng. The brothers successfully take back Lotus Pier. To break the deadlock with the Wen, Wei Wuxian retrieves the iron sword from the Tortoise of Carnage's cave and forges it into the Stygian Tiger Seal.