Well, for a chaos story fanfiction, you could do something like this. Imagine a story where a group of people wake up one day and find that all the laws of physics are in chaos. Gravity works randomly, and time is all messed up. They have to figure out how to survive in this topsy - turvy world. Or perhaps a fanfiction based on a popular book or movie where an unexpected event throws the original story into chaos. For example, if it was a Harry Potter fanfiction, a new dark magic could be unleashed that the characters have no idea how to combat. Also, a chaos story could involve a character from a different dimension accidentally entering another world and causing chaos just by their presence, as their powers or nature don't fit in the new world.
A great chaos story fanfiction concept could be centered around a city that suddenly experiences a total breakdown of order. All the social structures collapse, and people are forced to fend for themselves. The fanfiction could follow different groups of people, some trying to restore order, some taking advantage of the chaos for their own gain. Another idea is a fanfiction set in a space - faring civilization where a mysterious signal causes all the ship systems to go haywire, creating chaos in the middle of deep space. Crew members must then work together to fix the problems and figure out where the signal came from. And you could also have a fanfiction where a magical spell gone wrong in a wizarding school causes chaos among the students and faculty, with classrooms turning into strange landscapes and spells misfiring everywhere.
You could write a fanfiction where the setting of Chaos Walking is changed slightly. Instead of the usual post - apocalyptic world, it could be set in a parallel universe where the Noise is a positive thing that helps people communicate better rather than causing chaos. Or you could focus on a relationship in the story, like developing a romantic subplot between two characters who were just friends in the original.
A plot could involve them getting lost in a mysterious, enchanted forest. In this fanfiction, they have to rely on each other to find their way out, and along the way, they discover hidden powers within themselves and form a stronger bond.
One idea could be that Percy has unique powers given to him by Chaos. For example, he might be able to control the very fabric of the universe in small ways. Maybe he can manipulate time on a very limited scale, like slowing it down during a fight to gain an advantage.
Perhaps a chaos mage could create chaos within the ninja academies. They could make the training exercises go haywire, like turning simple target practice into a wild chase where the targets move on their own and attack the students. This would force the students, including Naruto, to think on their feet and develop new skills to deal with the unexpected chaos. It could also be a story where the chaos mage tries to use their magic to rewrite the history of the ninja world, but the ninja fight back to preserve their heritage.
One idea could be Percy facing a new chaos - themed villain who can manipulate time in a disorderly way. Percy has to find a way to break the time - loops the villain creates.
Perhaps Percy could be in a constant battle within himself. On one side, his normal demigod self with loyalty to his friends and Camp Half - Blood, and on the other, the chaotic side of him that wants to disrupt and change things. He might meet other 'children of chaos' and they could either be his allies or enemies. And his journey could involve learning about the true nature of chaos and how to use his powers for good, like protecting the world from a greater chaos that threatens to engulf it all.
One idea could be a crossover with the Warhammer 40K Imperium forces where a group of Chaos Space Marines infiltrate an Imperial stronghold. They could face off against Space Marines of the Ultramarines chapter, leading to intense battles and moral dilemmas for both sides. Another idea is a crossover with a fantasy setting like the Elder Scrolls. The Chaos Space Marines could find themselves in Tamriel, causing chaos among the different races and factions there. They might encounter the powerful mages or the warrior guilds.
One idea could be that Percy and Calypso find themselves in a strange new world within the chaos, where the rules of magic are all jumbled. They have to rely on each other's unique abilities to survive. For example, Percy's water - controlling skills and Calypso's nature - based magic might combine in unexpected ways to fend off the chaotic creatures they encounter.
One plot idea could be Percy being sent on a secret mission by the Chaos forces to infiltrate an enemy stronghold. He uses his skills and wits to gather intelligence without being detected.
A possible plot for 'Percy is a Son of Chaos' fanfiction could be Percy being sent on a mission by Chaos itself. This mission could be to restore balance in a part of the universe that has been thrown into chaos (ironically) by some dark force. Along the way, he teams up with some unlikely allies, some of whom are also children of primordial entities. They all have different motives and powers, and Percy has to learn to work with them while also coming to terms with his own identity as a son of Chaos.