The theme of misunderstandings is quite common too. For instance, Merlin might be caught doing something that looks completely different from what he's actually doing. Maybe he's using magic to heal a sick animal, but it looks like he's casting an evil spell. And then there's the theme of the magical creatures causing chaos. A tiny dragon that Merlin accidentally summons could end up stealing all of Arthur's shiny objects and Merlin has to chase it around the castle. These themes add a lot of humor to the fanfictions.
Often, there's the theme of Merlin being the unexpected hero in comical ways. He might defeat an enemy not by his powerful magic but by some silly accident. Like tripping over a stone and causing a chain reaction that knocks out the bad guys. There's also the theme of Camelot's court being turned upside down by Merlin's antics or the actions of other magical beings. The pomp and formality of the court contrasted with the chaos brought by magic - related events creates a lot of comical situations.
One big theme is the exploration of magic. In many Merlin female fanfictions, the female characters are either learning magic, or have a special connection to magic that is different from the male characters. For instance, a female character might have a more intuitive approach to magic. Also, the theme of friendship is present. A female character could form a strong friendship with Merlin or other characters like Guinevere, and this friendship is crucial in their adventures.
Power and responsibility are common themes. As Merlin becomes king, he has to handle the power he's gained while being responsible for his kingdom. Another theme is magic and its role in ruling. Since Merlin is a powerful sorcerer, fanfictions often explore how his magic affects his kingship, whether it's for protection or for the betterment of the kingdom.
One common theme is the loss of hope. As Camelot collapses, the characters often struggle with losing their faith in the future. Another theme is the test of loyalty. Friends may turn against each other in the face of chaos.
Another theme is the empowerment of female characters. In these fanfictions, the female characters usually break free from the traditional roles and show great strength and independence, especially in the context of their relationships.
A prevalent theme is the exploration of magic itself. How the magic in the Harry Potter universe and that in the Merlin universe are related or different. Also, destiny plays a role. Fanfictions often explore how their destinies are intertwined, whether it was meant to be that they meet and change the course of events in both their worlds.
One of the main themes is the conflict between Merlin's secret magic and the public perception in the royal court. There's also the theme of destiny. Merlin is often seen as having a great destiny in relation to the royalty. And love, whether it be platonic or romantic between Merlin and the royal characters, is a frequent theme. For example, in many fanfictions, Merlin forms a deep bond of friendship with Arthur that is almost like a brotherly love. His loyalty to Arthur and the kingdom is constantly tested by his need to hide his magic.
Magic is a very common theme. Since it's about Merlin's ritual, magic is at the core. It often shows how powerful Merlin's magic was through the ritual.
One common theme is the display of friendship. When Merlin has a fever, his friends, especially Arthur, often show deep concern and loyalty. Another theme is the exploration of Merlin's magic. Sometimes the fever is related to his magic in some way, like it being a side - effect of using a powerful spell.
Another theme is adventure. They are usually set in a magical world, so going on quests and facing challenges is a big part of it. For example, they might be on a mission to find a lost magical artifact. This allows for a lot of action and excitement in the stories.
Well, a major theme is power. Merlin already has magic, which is a form of power, and as an assassin, he has another kind of power. How he uses these powers together or separately is often explored. Also, the theme of betrayal is common. As an assassin, he might be betrayed or he might have to betray others. And there's the theme of survival. In the dangerous world of being an assassin, Merlin has to find ways to survive. This could involve using his wits, his magic, or his assassin skills.