It could also be that the Merlin fandom faced a lot of in - fighting or some negative events within the community related to Merlin. This could have demotivated fans from writing fanfiction, so it seemed like Merlin 'killed' it. For example, if there were disputes over what was considered acceptable fanfiction within the Merlin fandom, it might have led to a decline in the overall creation of fanfiction.
If Merlin is a show, it could be that the show's producers took legal actions against fanfiction, which effectively put an end to it.
Maybe the way the Merlin story evolved in its official form left no room for fan creativity. For instance, if all the possible storylines were neatly wrapped up in the official version, fans didn't feel the need or have the inspiration to write fanfiction anymore.
Merlin could use his magic to show Harry visions of a better future. By giving him hope, Harry might change his mind. For example, Merlin could show Harry how his actions in the future would lead to great good.
Meeting his father could have made Merlin more confident. Knowing his family background and having his father's presence (even if it was just in the fanfiction) might have given him a sense of belonging. He could also become more powerful, as perhaps his father passed on some knowledge or power to him.
One possible reason could be the extreme pressure he faces. Merlin has to constantly hide his magic in a world where it's feared and persecuted. This secrecy and the fear of being discovered might have built up to a point where he feels there's no way out. Also, his loyalty to Arthur might play a part. If he feels he has failed Arthur in some way, like not being able to protect him fully from threats, it could lead to such despair.
Arthur would likely be shocked and feel guilty. He might think that he has failed Merlin in some way, not realizing the full extent of Merlin's inner turmoil. He would probably become more protective and try to find out what made Merlin feel this way.
He could become a Dark Lord due to betrayal. If someone he trusted deeply, like Arthur perhaps, turned on him because of his magic, it might push him over the edge.
In some fanfictions, Konan might use her origami techniques in a highly lethal way. Maybe she creates a large number of explosive paper bombs and traps Obito in a confined space, detonating them all at once to overpower his defenses and kill him.
In some fanfics, Merlin might have tricked Arthur or convinced him it was for the kingdom's safety.
If Merlin forgets, it can create a lot of suspense. The other characters might not immediately realize what has happened, and they'll be confused by Merlin's changed behavior. This can lead to misunderstandings and tension within the group. For instance, if Merlin forgets his magical abilities, he might accidentally expose his powers in dangerous situations because he no longer has the knowledge to control them properly.
Some might be shocked. For instance, Morgana, who has her own complex story arc, may be taken aback by how fans rewrite her motives in fanfiction. She might not expect certain sympathetic portrayals.
Maybe in the fanfiction, Uther discovers the creativity and the different perspectives on his world and characters, and he sees value in it. He might be a more open - minded version of himself in the fan - created stories.