Some of the knights could be a bit jealous. Immortality means having an infinite amount of time, and they might envy Merlin for that. But at the same time, they would also be very protective of him, knowing that his immortality could make him a target.
Well, initially there would be disbelief. But as they come to terms with it, their relationship with Merlin would change. They would start to see him as an even more valuable asset to Camelot. His immortality would give him the ability to gain knowledge and skills over centuries, which could be very useful for Camelot's future. So, they might start to rely on him more, not just for his magic but also for his long - term perspective on things.
The Avengers would be furious. Natasha would use her spy skills to find out all about the bullies without them even knowing. Thor might be a bit more direct, perhaps showing up at the school in his full Asgardian glory to scare the bullies straight. Clint could offer to teach Peter some self - defense moves so he can stand up for himself.
Arthur could also feel betrayed. He has trusted Merlin completely, and finding out about his magic might make him think that Merlin has been hiding something huge from him all this time. However, depending on how the fanfiction is written, he might eventually come to understand Merlin's reasons for secrecy.
Sasuke might be a bit jealous at first. He's always been competitive with Naruto, and seeing Naruto in a special and elite unit like ANBU could trigger that jealousy. He might try to prove that he's just as good or better. Sakura, on the other hand, would probably be worried. She cares a lot about Naruto and ANBU missions are often dangerous.
Well, first of all, they would be shocked. I mean, Stiles is like family to them. Then, they would probably rally around him. Lydia might use her intelligence to figure out a way to help Stiles deal with the emotional trauma. Derek, with his brooding nature, would become super protective, maybe even train Stiles to defend himself better. And the rest of the pack would offer their support in different ways, like providing a safe place for Stiles to stay or just being there to listen when he needs to talk.
Some Avengers might be protective. For instance, Captain America could immediately start giving Peter advice on how to better handle his dual identity and keep himself safe. He might offer training sessions to help Peter improve his skills as Spider - Man.
The more superstitious knights might think that Merlin has called upon some real evil spirits and become very worried. They might start praying or asking Merlin to make the 'spirits' go away. And some might be so scared that they avoid Merlin for a while afterwards, not wanting to be the target of his next scare.
Some Avengers might be surprised. Tony Stark, for instance, might be like 'Kid, you're younger than I thought!' and then start to adjust how he mentors Spider - Man. He could become more cautious about the risks he lets Spider - Man take.
One popular Merlin Knights fanfiction could be those that explore the knights' adventures before Merlin joined them. For example, stories might focus on how they met and formed their initial bond. Another could be the ones where Merlin uses his magic in unique ways to save the knights during a particularly dangerous quest. There are also fanfictions that delve into the relationships between the knights themselves, like their rivalries and deep friendships.
One popular story could be about Merlin secretly having more powerful magic than anyone realizes and using it to save the knights in a very dangerous quest. For example, he might be able to conjure up powerful shields to protect them from a dragon's fire.
One common theme is loyalty. The knights' loyalty to Merlin and vice versa is often explored. It shows how they stand by each other through thick and thin.