In a fanfiction where Percy lives in the underworld, he could be on a mission to redeem the souls of some of the most heinous criminals. This would be a huge task as the underworld is filled with souls that have committed great evils. He would have to use his wits and powers, and maybe even make some difficult bargains with the rulers of the underworld to achieve this goal.
One possible storyline could be Percy having to deal with the constant gloom and the various creatures that lurk in the underworld. He might try to find a way to bring some light or hope to the place. For example, he could use his powers to make small areas more habitable for the lost souls there.
Perhaps Percy discovers a hidden part of the underworld that no one else knows about. This could lead to him finding secrets about the gods or even a way to change the nature of the underworld itself. He may encounter new and strange creatures that are unique to this hidden area and form alliances or face new enemies.
A practical answer is Chapter 108, because it turns the idea into a concrete scene. The chapter opens with In a glamorous Michelin three-star restaurant, Su Yinwan and Shang..., adds pressure through Jiang Yan, "...." Did he chew 20 times just now?, and ends on Hey, I've been waiting for you for.
If you want the clearest chapter reference, go to Chapter 112. Early on, These five people are supposed to be at odds.; later, the chapter leans on When did they become so in sync?] [I'm dying of laughter hahaha why is....
Look to Chapter 145 for the clearest answer. It begins with Chixia Village was located in a remote area with a backward economy, so..., keeps building through The villagers' daily meals were mostly about filling the stomach, so the..., and lands on What about it?" "That's unfortunate," said Jiang.
If you want the clearest chapter reference, go to Chapter 143. Early on, Is there really such delicious fish soup in the world?; later, the chapter leans on Sister Li, you are too awesome!" The fish soup was not only fresh and....
The best chapter pointer here is Chapter 164, "Congratulations to Jiang Yan for scoring one point!". It opens with Damn, the production team is so shady, they're still doing a live... and closes on The current Jiang Li did indeed make him see her in a new light, to some....
Chapter 121 is the strongest chapter-level answer because it starts from Seeing that Wen Jiaojiao's condition had improved significantly, Director... and follows through on You're supposed to be a man who conquers mountains!] Experienced and....
A practical answer is Chapter 112, because it turns the idea into a concrete scene. The chapter opens with These five people are supposed to be at odds., adds pressure through Do you remember that bowl of Mushroom Soup?" Jiang Li smiled, "Your..., and ends on [Hahahaha why is the Princess starting.
Look to Chapter 112 for the clearest answer. It begins with These five people are supposed to be at odds., keeps building through When did they become so in sync?] [I'm dying of laughter hahaha why is..., and lands on [Hahahaha why is the Princess starting to look disappointed?] [Help, even....
The best chapter pointer here is Chapter 170, "This Family Will Fall Apart Without Jiang Li". It opens with Watching the two who had long remained silent, the PD shifted his position... and closes on [Didn't the other guests also do farm work in the rain all morning, isn't....
If you want the clearest chapter reference, go to Chapter 151. Early on, Now it was Zhang Cheng's turn to be confused.; later, the chapter leans on The problem lies with He Yun?. By the close, I will have my assistant pay the bill., and the chapter closes with Was he...