Episode Summary
Wu Zhen challenges and defeats the far more experienced Elder Hui in a forbidden duel by turning his desperate, rule-breaking lightning attack against him to unlock her own power. Victorious but severely wounded, she returns home and collapses into the care of Mei Zhuyu, who begins to grow suspicious of her true identity.

Spoiler Alert
Episode 12 of Moonlit Reunion begins with Wu Zhen making a huge call: she's challenging Elder Hui to a Life and Death Duel. This isn't just any fight; it's a forbidden ritual. Elder Hui, unimpressed, easily breaks his chains and unleashes his power, creating a massive dueling field in the sky above the Demon Market. All the demons below are watching, totally stunned.
Liu Taizhen is furious, thinking Wu Zhen is being way too reckless. The Life and Death Duel is an ancient, forbidden technique meant to be a last resort to stop corrupt leaders. A Cat Duke fighting an Elder like this is unheard of. When others rush to Liu Taizhen for a plan, her answer is cold: if Wu Zhen dies, she will personally kill Elder Hui to avenge her.
The night before the duel, Wu Zhen is trying to clear her head by fishing alone. Mei Zhuyu finds her, clearly wanting to say something important. But he keeps hesitating, remembering his master's warning that people from Changxi Palace can't get emotionally involved. He can't bring himself to confess his feelings. Wu Zhen gets annoyed by his silence, tells him she has plans with another guy, and just leaves him standing there.
Meanwhile, Mei Si is reading a book called "Notes on Monsters and Ghouls" and gets stuck on a line about the new moon. Xuanhui explains that on a moonless night, evil energy is at its peak, which is why it's the perfect time for demons to settle their scores.
The duel starts. It's Wu Zhen, with only ten years of training, against Elder Hui, who has a century of power. At first, it looks like everyone expects: Wu Zhen is getting beaten down. But no matter how many times she's knocked down, she forces herself back up. Seeing her resilience, Elder Hui decides to end it by using his ultimate weapon. Wu Zhen meets his attack with her own, and the two are locked in a massive battle.
Realizing he might actually lose, Elder Hui cheats. He breaks the duel's barrier to summon divine lightning from the heavens—a major violation of the Demon Market's laws. He's so desperate to win that he doesn't care about the punishment. The lightning traps them both. The Wordless Book tries to intervene but is thrown back by the storm's power. Elder Hui thinks he's won, but the plan backfires. Instead of being destroyed, Wu Zhen absorbs the lightning's power, breaking through her own limits and revealing her true form as a giant cat demon for the final showdown.
In the end, Elder Hui is defeated. He can't understand how his hundred years of cultivation lost to her. Wu Zhen tells him that winning isn't just about how long you've trained. Because he broke the rules, she strips him of all his powers, turns him into a mortal, and banishes him to the human world to live among the people he once harmed.
Even though she won, Wu Zhen is seriously injured. All she can think about is her promise to Mei Zhuyu that she'd come home. She manages to drag herself back, finding him still waiting up for her. Just as she reaches him, her strength gives out, and she collapses unconscious into his arms.
In another part of the city, Liu Taizhen comes home to find Mei Si asleep by her door. He came to protect her during the dangerous new moon night and fell asleep waiting. She's a little touched by the gesture. Back at home, as Mei Zhuyu takes care of the feverish Wu Zhen, he starts putting the pieces together about her past and begins to suspect who she really is.