He would probably interact with Dumbledore a lot. They are both very powerful wizards and could share a great deal of magical knowledge.
Well, he might bring his powerful magic skills to the Order. Maybe he could use his magic to create new defensive spells for the Order's headquarters.
In a Merlin - joins - the - Avengers fanfiction, there could be some really interesting scenarios. Merlin's magic could add a whole new dimension to the Avengers' battles. He could use his magic to heal the Avengers quickly or create illusions to deceive their enemies. Maybe he'd have some clashes with Tony Stark at first because of their different approaches to problem - solving, but eventually they'd learn to work together.
The Avengers would also have to adjust to the social and cultural norms of Camelot. They can't just barge in and start making demands. Merlin would have to act as a mediator between the two groups. He would explain to the people of Camelot that the Avengers are there to help, and at the same time, he would make sure the Avengers understand the importance of respecting Camelot's traditions. This interaction would create a lot of interesting storylines and character development opportunities.
Merlin, being a very wise and sometimes mischievous wizard, would likely be intrigued by Eragon's dragon - related powers. He might start by observing Eragon and Saphira from a distance. Eragon, on the other hand, would be cautious at first, as he doesn't know Merlin's intentions. But once they start talking, Merlin could share some of his knowledge about magic, which would be really valuable for Eragon.
Merlin and Frodo could have an interesting interaction. Frodo, burdened with the One Ring, might seek Merlin's advice on how to resist its power. Merlin, having dealt with dark magic before, could offer some insights.
Since Hermione is highly skilled in academic magic, she could use her knowledge to analyze Merlin's magic. Maybe she discovers ways to enhance his spells or make them more efficient. Merlin, with his natural and powerful magic, could help Hermione break free from some of the limitations of the Hogwarts magic system. For example, he might show her how to draw magic from sources other than a wand, which could be a game - changer for her.
A sense of adventure would be in Merlin's story. He has been on many quests and journeys. He might talk about traveling to far - off lands in search of a solution to a problem in Camelot. He could describe the different landscapes he saw, from snow - covered mountains to vast deserts. And of course, there would be elements of good versus evil, as Merlin constantly battles against the forces of darkness to protect the light in Camelot.
Perhaps some of the snooty nobles who look down on Merlin and constantly try to get him into trouble. They could be making fun of his clumsy ways one too many times and he just snaps and hits them with a shoe. It would be a moment of satisfaction for the readers who don't like those arrogant characters.
Obviously, Harry himself is very important. Then there's Sirius Black, who could play a big role in guiding Harry within the Order. Dumbledore would also be crucial as the leader of the Order.
The magic in Merlin's world is often more traditional, based on spells and incantations. In the Trollhunters' world, the magic seems more innate to the trolls. If they were to interact, Merlin's spells could potentially enhance or disrupt the natural magic of the trolls. For example, a spell of his might accidentally block a troll's ability to use its natural camouflage magic.