Mo Yuan puts Ling Yu in charge of leading troops on the front lines and has Si Yin stay in the middle with him. The night before the first battle, Si Yin stares out at the river valley that will serve as their battlefield and thinks about how it will soon be filled with corpses. Mo Yuan tries to ease her mind about the battle, saying it will lead to peace. He teaches her how to use the Donghuang Bell to seal power. Even though it’s a dangerous spell, she’s the most powerful of his disciples and capable of doing it. She wonders if he knows her true identity.
Zhe Yan fetches his Fuxi qin from where he stashed it under Kunlun Mountain.
The battle between Celestial and Demon begins. The Celestials’ first formation falls sooner than expected.
Ling Yu fights against Li Yuan in the thick of the battle and is soon surrounded. Si Yin sees what’s happening and flies in to help, but she’s too late. Ling Yu falls to his knees after being shot full of arrows at close range multiple times. Now, Si Yin is the one who is alone and surrounded and Li Yuan will not let her leave.
Li Jing enters the battle even though he’s supposed to hang back with his sister. Yan Zhi guesses that Si Yin is the one he loves. He flies in to stand between Li Yuan and Si Yin, saying that as the person who helped counter the Celestial Clan’s battle strategy, he should at least be entitled to save someone that he wants to save. Li Yuan acknowledges that Xuan Nu did do a good job stealing the tactical maps from Kunlun. Si Yin looks betrayed yet again. Li Jing tries to explain himself, but a man zaps in with a phoenix, grabs Si Yin and Ling Yu, and then teleports them all away.
There’s nothing that can be done for Ling Yu. Mo Yuan orders for his body to be taken back to Kunlun. He tries to comfort Si Yin, who sobs that this is all her fault. If she had found out sooner, then maybe Ling Yu wouldn’t have died. She shares that Xuan Nu has stolen their tactical plans. The war leaders look crestfallen. If Qing Cang has their plans, then their defeat is certain.
Bai Zhen was the one who flew in to retrieve Si Yin and Ling Yu. Because he has no stake in the battle as a member of the Fox Clan, he takes Si Yin outside while the other discuss what to do.
The news from the battlefront is all bad. Mo Yuan comes up with a new, risky plan to turn the tide in their favor. It involves sacrificing 10,000 troops as bait to draw away half of the Demon forces. Yao Guang volunteers to lead them, as it’s the only way to make the ruse convincing.
Si Yin blames herself for letting Xuan Nu stay at Kunlun. The only reason she didn’t kill Xuan Nu is because of their sister-in-law (who is Xuan Nu’s half-sister). Bai Zhen points out that by that logic, he’s the one at fault for asking her to take in Xuan Nu. Their sister-in-law is actually grateful to Si Yin for getting Xuan Nu married off. But now that Xuan Nu is officially part of the Demon Clan, Xuan Nu is free to kill her the next time she sees her. That’s what she deserves.
Mo Yuan needs two more commanders to lead his troops. Si Yin volunteers and her brother does as well. Other than Mo Yuan, he is the next most powerful immortal present on their side of the battle.
Mo Yuan’s strategy works and the Celestials manage to surround Qing Cang, calling for his surrender. Rather than surrender, Qing Cang pulls out the Donghuang Bell and tosses it into the sky. Si Yin flies up to try and stop him, but Qing Cang forces her back. Mo Yuan hops up after her and pushes her down to safety. The Donghuang Bell opens up and starts pulling soldiers from both sides into the sky.
Mo Yuan starts to deactivate the bell, but Qing Cang attacks him. They fight and eventually Mo Yuan manages to kick Qing Cang into the bell. The Donghuang Bell is still trying to suck in all living beings. Mo Yuan looks at Si Yin, says, “Wait for me,” and then flies in.
After a blinding blast of light, the bell falls into the river and Mo Yuan’s body floats through the air back to land. Si Yin catches him and sobs over his body. All the other disciples fall to their knees and mourn.
Li Yuan offers the Celestials a letter of surrender. Now that his father is sealed in the bell, he has no reason to want the Celestials as his enemy. But Si Yin is furious and wants to get vengeance and kill the whole clan. Yan Zhi tries to reason with her and Die Feng and Zi Lan try to hold her back, but Si Yin refuses to back down. In the end, Bai Zhen knocks her out using one of her pressure points and tells the Celestials to return to Kunlun.
Siming informs the Donghua Emperor that Mo Yuan’s soul has departed after he sacrificed himself to stop the bell. Donghua looks more surprised than we’ve ever seen him, then tells Siming to go to the Ziming Palace in the Demon Realm.
Li Jing drinks and broods in the Demon Realm, angrily striking Xuan Nu and throwing her aside when she brings him some fruit. Xuan Nu doesn’t understand why he’s treating her this way and repeats her previous groveling, reminding him that now that she betrayed Kunlun so thoroughly, he is the only one she can rely on. Li Jing responds that she’s relying on the wrong person. Now that his brother has the throne, it’s only a matter of time before he has him killed.
Siming visits Li Jing and says he can help him be the Demon Monarch. Li Jing isn’t interested, but Siming reminds him that his brother will likely have him killed and that there’s still the matter of his mother’s death between them. Xuan Nu eavesdrops and smiles to herself.
The golden lotus in the lotus pond at Kunlun withers.
Si Yin wakes up in Mo Yuan’s cavern by the lotus pond. She rushes to Mo Yuan’s body then turns to Zhe Yan, asking when he will wake up.
CGI battle! My worst nightmare. The battle scenes leave something to be desired, but this isn’t really the kind of show where battle and fighting sequences are the focus, I guess. It is pretty metal that Bai Qian/Si Yin fights with a fan while everyone else is out here with swords. It seems pacifist, but ironically she’s probably the most bloodthirsty of them all if you get on her wrong side… or maybe she just talks a big talk?