Another interesting idea is a high school competition between different cabins. Instead of regular sports, they could have contests like who can best use their godly powers in a non - destructive way. It would be a great way to show off the different abilities of the demigods and also create some friendly rivalries.
A great plot for a 'Percy Jackson at School' fanfic would be Percy competing in a school - wide competition that is secretly a test by the gods. The tasks in the competition could be related to the skills he has learned in his demigod adventures, like sword - fighting or outsmarting a maze - like obstacle. Also, he could befriend a mortal student who starts to suspect there is something different about Percy and his friends, and Percy has to decide whether to reveal the truth or keep the mortal in the dark.
Perhaps there's a prophecy that involves both Percy and Artemis in the high school. It could be about a hidden power within the school that only they can unlock together. They have to navigate high school politics, friendships, and enemies all while trying to figure out the prophecy and save the day.
One idea could be Percy having to deal with a new type of mythical creature that has infiltrated Goode High School. Maybe a group of mischievous satyrs that are causing chaos in the school cafeteria by stealing all the food and Percy has to use his skills to stop them without revealing his true identity to the normal students.
One idea could be Percy having to hide his demigod powers at high school while dealing with a bully who unknowingly has ties to a minor Greek god. This would create a lot of tense drama situations.
Perhaps there's a mystery at Ares High School where strange things keep happening, like students getting sudden bursts of uncontrollable strength. Percy, suspecting it has something to do with Ares, investigates and discovers an ancient artifact hidden on campus that's causing the chaos. He then has to find a way to stop it without getting caught by the school authorities or Ares' minions.
One idea could be a story where Percy has to deal with a new mythical creature that shows up at school. Maybe it's a mischievous imp that keeps causing chaos during classes and Percy has to figure out how to send it back to where it came from without getting in trouble with the teachers.
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.
Another interesting concept is a crossover of the storylines. The prophecy in Percy Jackson could somehow be related to the events in Undertale. For instance, the hero's journey in both worlds might be intertwined, with Percy and Frisk having to work together to save both their universes from a common threat.
One idea could be exploring the lives of the children of the original demigods. For example, how they deal with the legacy of their parents' great deeds and also face new threats. Another could be a time - travel fanfic where a modern - day demigod goes back in time to the era of the first Percy Jackson adventures and has to interact with the younger versions of the characters.
Perhaps a story where a Nephilim is sent to the Percy Jackson world to learn about different forms of power. This Nephilim could initially be a bit of an outcast in their own world due to their unique abilities, and in the Percy Jackson universe, they discover new ways to use their powers and form unexpected friendships.