You could also do a time - travel fanfic within the Chaos Trilogy universe. A character goes back in time to try and prevent a major catastrophe that happened in the original trilogy. This would involve them having to interact with their past selves and deal with the consequences of changing the past.
One idea could be exploring the backstory of a minor character in the 'chaos walking' universe. For example, a sidekick who has some hidden powers or a past connection to the main antagonist. Another plot could be a time - travel scenario where a character goes back in time to change a crucial event in the 'chaos walking' story, which then has a ripple effect on the entire world. Maybe also a plot where the characters find a new planet that has a completely different form of the 'noise' and they have to adapt to it.
One interesting plot idea could be a new and powerful villain emerging in the 'naruto of chaos fanfic' world. This villain could have a unique ability that challenges Naruto and his friends in ways they've never faced before.
A possible plot is that Tikal and Chaos meet in a dream realm first. In this realm, they gradually understand each other's true natures. As they keep meeting in this way, they start to form an unlikely bond. When they finally meet in the real world, they are already friends and work together to restore balance to the chaos emeralds' energy.
One idea could be a quest to find all the Chaos Emeralds in a post - apocalyptic world where the power of the emeralds is the key to restoring order. Another could be a story where a new character discovers they have a special connection to the Chaos Emerald Z and must learn to control its power to defeat an ancient evil.
One idea could be Percy's struggle to balance his new role as the 'Husband of Chaos' with his loyalty to his friends from Camp Half - Blood. Maybe he has to make difficult decisions that affect both the chaotic realm and the mortal world.
Well, in some 'chaos naruto fanfic', there might be a different origin story for Naruto. Instead of the normal one, it could be that he was born with a special connection to a chaos realm, which shapes his journey and his relationships with other characters in a whole new way. This would add a lot of depth to his character and the overall story.
One idea could be to explore the origin of the Angel of Chaos. Maybe it was once a regular angel who was corrupted by a powerful dark force. This could lead to a story about its journey from grace to chaos.
One idea could be exploring the backstory of Bartimaeus in more detail. Maybe how he first became a djinni and his early experiences in the spirit world.
A great plot for Grisha Trilogy fanfiction might be a time - travel story. Imagine a character from the present in the Grisha world going back in time to the early days of the Grisha. They could then change or influence historical events. Or perhaps a fanfic about a Grisha who has lost their powers and has to find a way to regain them without the help of the traditional Grisha methods. It could involve a journey across different lands in search of a mysterious cure.
One idea could be exploring a side character's backstory in more detail. For example, the character who is a minor in the original trilogy but has a lot of potential for a deeper story. Maybe they have a secret past that ties into the main plot in unexpected ways.