A great plot idea is to have your insert be a time - traveler who accidentally ends up in the Percy Jackson universe. They know some future events and try to prevent a great disaster from happening in the world of demigods. Along the way, they have to convince Percy and the others to trust them, which is not easy since they seem so out of place.
You could make your inserted character a half - blood who has been living in the mortal world without knowing their true identity. They get drawn to Camp Half - Blood by a strange force. Once there, they discover they have a connection to an important prophecy. Their presence changes the dynamics of how Percy and his friends approach fulfilling the prophecy, adding new twists and turns to the story.
One idea could be that your inserted character is a new camper who has a special ability related to an ancient and forgotten Greek magic. This character then helps Percy and his friends in a battle against a revived mythological villain that is more powerful than any they've faced before.
A possible plot for a Percy Jackson Titan self - insert fanfiction is that the self - insert is a Titan who was imprisoned by the gods long ago. They manage to break free and find themselves in the modern world of Percy Jackson. Instead of seeking revenge immediately, they decide to observe and learn about the new world. Along the way, they befriend Percy and the gang, but their true identity is slowly revealed. This leads to a conflict as some demigods want to imprison them again, while others believe they can be an ally. The self - insert then has to prove their worth and intentions.
In a fanfic, perhaps Percy and his friends accidentally stumble upon Medusa's lair while on a quest. But instead of immediately attacking, Medusa offers them a deal. She says she will give them a valuable clue to complete their quest if they help her get revenge on one of the minor gods who wronged her in the past. Percy and his friends then have to decide whether to trust Medusa or not.
One plot idea could be Percy emerging from a battle with a water monster, dripping wet and having to find shelter in an unexpected place, like a hidden cave that has some ancient prophecy written on the walls. Another could be Percy getting drenched during a wild storm at Camp Half - Blood and then discovering a new power related to water while in that dripping wet state. Maybe he's dripping wet after being pushed into a magical pool and when he comes out, he can communicate with sea creatures in a new way.
One idea could be the self - insert character discovers they have a unique power related to Hades that no one else in the Percy Jackson world has. Maybe they can control a special type of underworld creature that hasn't been seen before. This could lead to a series of adventures where they have to prove themselves to the other demigods and also to Hades himself.
Another plot could involve Percy's friends getting accidentally transported to a different realm in the Percy Jackson universe. They have to rely on their friendship and the skills they've learned from Percy to survive and find their way back. For example, they might end up in the Underworld and have to navigate past various challenges without Percy at first.
One idea could be a mortal accidentally stumbling into Camp Half - Blood and having to adapt quickly to the world of demigods. Maybe they have some hidden power that only reveals itself in this new environment.
One idea could be to create a new quest within the game world. For example, Percy and his friends have to retrieve a powerful artifact that was stolen by a new type of monster. This could involve exploring new areas of the game, like a hidden underwater city that has never been discovered before. Another plot could be a tournament in the game where demigods from different cabins compete against each other in various challenges. This would show off their different skills and powers. A third idea is that there's a glitch in the game that's causing real - world problems in the Percy Jackson universe, and they have to figure out how to fix it before it's too late.
One plot idea could be Gaea's redemption. In the original series, she was a major villain, but in a fanfic, she could be given a chance at redemption. Maybe Percy and his friends discover that Gaea was being controlled by a more powerful and malevolent force all along, and they have to work with her to defeat this greater evil.
In a Percy Jackson Tartarus fanfic, a great plot could be centered around Tartarus corrupting the very essence of Percy's powers. He starts to lose control of his water - based abilities and instead they become tainted with the darkness of Tartarus. Percy then has to go on a journey within Tartarus to find a way to cleanse his powers, all while being hunted by the most dangerous creatures that lurk in the abyss.
A really interesting plot would be if Percy lost his memory and ended up in a mortal town. He has to figure out who he is on his own while still being hunted by some old enemies. The gods are aware of his situation but can't interfere directly because of some ancient rule. So Percy has to rely on his instincts and any small clues he can find about his past to get back to his normal self and his life at Camp Half - Blood.