Well, you could try looking on fanfiction.net. There are often some great Percy Jackson fanfics there. Just search for 'Subject X' within the Percy Jackson section. You might find some really creative stories that explore new aspects of the Percy Jackson universe related to Subject X.
One thing that makes Percy Jackson popular in fanfiction is the unique world - building. The mix of modern - day settings with ancient Greek mythology is really cool. Fanfiction writers can explore this world further. Another reason is Percy's character arc. It's something that can be continued and developed in fanfiction. For instance, his growth from a confused demigod to a hero can be explored in different ways.
One idea could be that Percy is secretly a test subject for a new type of magic-infused weapon. The gods are using him to see how a demigod can handle the power without going berserk. Another could be that he's a test subject for a time - travel experiment by the camp's resident genius, and he has to deal with the consequences of messing up the timeline. Maybe he's also a test subject for a new type of healing potion that has some really strange side effects, like making his hair turn blue or giving him the ability to talk to fish in a really posh accent.
Maybe it's a corrupted god. Let's say Hades in this case. He's always been a bit of an outcast among the gods. He decides to use Percy as a test subject in a plot to gain more power in the underworld. He subjects Percy to all sorts of trials and tests that are meant to break him down and extract his power. Percy has to fight against Hades' dark magic and find a way to escape his clutches.
A really good 'Percy Jackson x Clarisse Fanfiction' is 'When Percy and Clarisse Train Together'. In this one, they are forced to train together and through the process, they discover new things about each other. They start to respect each other more and it's a great read for those who like character - development - focused stories.
One aspect of 'Percy Jackson x Gaia Fanfiction' could be the unique power dynamics. Percy has his own set of powers from being a demigod, and Gaia is an extremely powerful primordial goddess. Their interaction in fanfiction might explore how Percy, with his courage and skills, contends with Gaia's all - encompassing power. It could also delve into the moral and ethical implications of Percy's relationship with such a powerful and ancient being.
Percy is definitely one of the most popular. Since he's the main character, fans like to explore different versions of him through transformation. For example, seeing him as a different mythical creature or having a different gender can lead to really interesting stories. Another popular one is Annabeth. Her intelligence and strong personality make her a great candidate for transformation. Fans might be interested in seeing how she'd handle a physical or gender transformation. Grover is also popular. Given his satyr nature, there are a lot of possibilities for further transformation, like turning him into a full - blown forest spirit or something more powerful in the nature - related realm.
The theme of sacrifice is also quite common. Sally has already made sacrifices for Percy in the original series, and in fanfiction, this can be exaggerated or explored further. It could be something as simple as sacrificing her own comfort for Percy's well - being, or more extreme sacrifices in the face of greater threats. Additionally, the theme of Percy understanding Sally's sacrifices and how it affects his view of her as a mother and a person is also often explored in these fanfictions.
For Percy, his loyalty and sense of adventure can be emphasized. He could be the one to initiate contact with Elsa, seeing her as a new and exciting mystery. His skills in combat and his ability to think on his feet would come in handy when they face challenges together. For Elsa, her growth from a withdrawn and fearful queen to someone more open and trusting can be shown. Meeting Percy, who is so different from the people in her world, could be a catalyst for this change.