One idea could be that the descendants' magic somehow gets intertwined with the Avengers' technology. For example, Mal's spell - casting could start affecting Iron Man's suit, causing glitches and unexpected behaviors. This would force the two groups to work together to figure out how to separate the magic from the tech.
A cool plot could be that some of the Avengers' powers get passed down to the descendants in a strange way. For instance, Thor's lightning power starts manifesting in one of the descendants. This causes a stir among both groups. They must then figure out why this is happening and how to control this new - found power. It could also lead to some interesting character dynamics as the descendants learn from the Avengers how to use these powers responsibly.
Maybe the Avengers find themselves in the world of the descendants. They have to adapt to the different rules there, like the use of magic and the social hierarchy. The descendants, in turn, are both in awe and a bit scared of these powerful superheroes. They could team up to fight a common enemy that is threatening both their worlds, like an ancient evil that is drawn to the combined power of magic and advanced technology.
Maybe there is a new character, a brilliant scientist, who has developed a dangerous weapon. Shi - Jin and Mo - Yeon have to team up with their friends to stop this weapon from being used, while also dealing with the scientist's personal vendetta against the military. This would add a lot of action and suspense to the fanfiction.
An interesting plot for Disney Descendants OC fanfiction could be an OC who is a spy from the Isle of the Lost sent to Auradon. But during their time there, they start to question their loyalty to the villains. They make friends with the Auradon kids and see the good in their way of life. This creates an internal conflict for the OC. Or, the OC could be an artist who uses their art to bridge the gap between the two worlds. Their art could be a form of magic that can show people the truth about both the Isle and Auradon. Also, an OC with a unique form of magic related to nature could come to Auradon and help solve environmental problems there, while also facing discrimination from some of the more 'proper' Auradonians.
One idea could be a story about a young descendant who discovers a hidden power within the Dragon Hall. Maybe they can communicate with ancient dragon spirits that no one else can, and this power helps them solve a mystery that has been plaguing the descendants for generations.
Another idea is that the father of Evie's baby is an unexpected character. This could create a lot of drama and tension as Evie tries to figure out how to tell the person and how they will both deal with the situation. And it could also lead to some interesting character development for both Evie and the father - to - be.
Another idea is that they both get lost in a mysterious part of Auradon that has been long forgotten. They have to work together to find their way back. Along the way, they discover secrets about Auradon's past that could change the way they view the place and their place in it. This journey would also strengthen their bond as they depend on each other for survival.
One idea could be a character from Naruto ending up in the Descendants' world. For example, Naruto himself could be transported there. He might use his ninja skills to deal with the challenges in the Descendants' world, like facing off against the villains in a very different way compared to the Descendants' characters. Maybe he'd use his shadow clone jutsu to confuse the bad guys or his Rasengan to take on powerful foes.
One idea could be that the characters from Descendants end up in the world of Jessie by some magical mishap. Mal could use her magic to help Jessie deal with some of the difficult kids she babysits, like when they get into trouble at school. Another plot could be that the kids from Jessie visit the Isle of the Lost out of curiosity and try to bring some positive change there. Maybe they start a music club or something similar to engage the villain kids in a more positive activity.
Perhaps a plot where Mal and Carlos discover a hidden part of Auradon that has a connection to their pasts on the Isle of the Lost. They have to keep it a secret from everyone else in Auradon while they explore it together. Along the way, they face challenges that test their loyalty to each other and to Auradon.
One idea could be that Mal struggles with her new role as Ben's girlfriend and future queen. She might feel pressured by the expectations of Auradon society. Another could be a story where an old enemy from the Isle of the Lost tries to break them apart by causing misunderstandings between Mal and Ben.
One idea could be that a character from 'Once Upon a Time' (OUAT) accidentally travels to the world of 'Descendants'. For example, Emma Swan could end up there and have to deal with the different rules and characters. Maybe she tries to help some of the 'villain kids' in 'Descendants' to see that they don't have to follow in their parents' footsteps, just like she often helped people in OUAT find their true selves.