One common theme is the struggle with identity. Since Percy is usually the son of Poseidon in the original series, making him the Son of Hades in fanfiction often leads to him dealing with a new sense of self. Another theme is power and its consequences. Hades has a lot of dark and powerful abilities, so fanfictions might explore how Percy copes with having access to such powers.
Friendship is also a big theme. How Percy's relationships with his friends like Annabeth and Grover change when he has this new connection to Hades. It could be that they are more wary of him, or he has to prove himself all over again. And of course, there's the theme of the underworld. Fanfictions might explore Percy's new relationship with the underworld, the creatures there, and his role in that realm.
A practical answer is Chapter 46, because it turns the idea into a concrete scene. The chapter opens with Upon hearing this, everyone but Jiang Li perked up with high alert., adds pressure through There must be some mistake with the crew's calculation, I demand a..., and ends on Did you calculate.
If you want the clearest chapter reference, go to Chapter 56. Early on, Lei Shen originally had no idea about the trending topics on Weibo.; later, the chapter leans on He had been busy renovating his studio for a while and hadn't even had....
Chapter 56 is the strongest chapter-level answer because it starts from Lei Shen originally had no idea about the trending topics on Weibo. and follows through on At this moment, Lu Xingchao was still in the dark..
Look to Chapter 65 for the clearest answer. It begins with Several minutes later, the room remained silent., keeps building through The cameraman then discovered that Jiang Li's door wasn't properly shut,..., and lands on What's the deal with these two?.
The best chapter pointer here is Chapter 49, "Mysticism Girl Jiang Li". It opens with My phone!!!" Jiang Yan's roar echoed continuously through the mountains in... and closes on Thinking this, Jiang Yan marched forward, pulled Jiang Li down from her....
Look to Chapter 70 for the clearest answer. It begins with So, under the curious gazes of everyone, Jiang Yan strutted up with his..., keeps building through He didn't even take off his sunglasses before he started reading into the..., and lands on He Yun was also surprised as he looked towards.
Chapter 43 is the strongest chapter-level answer because it starts from The moment He Yun willingly sat next to Jiang Li and even took off his... and follows through on Just as she turned her gaze away, the other party huffed and withdrew her....
If you want the clearest chapter reference, go to Chapter 53. Early on, Night had fallen over Chixia Village, eerily void of any human sounds.; later, the chapter leans on Jiang Li followed the village chief's wife down a narrow path leading to....
A practical answer is Chapter 60, because it turns the idea into a concrete scene. The chapter opens with What's with Jiang Yan, treating his own sister Jiang Li like this?" "He..., adds pressure through Jiang Yan, are you that lacking in confidence?, and ends on And in traditional characters?".
Look to Chapter 63 for the clearest answer. It begins with During those seven days, he thought he had completely escaped from that..., keeps building through But now it seemed he hadn't., and lands on It was already past midnight, but the conference room at Xingmei....