Some old Merlin fanfiction that stands out are the ones that rewrite key events in the series. For instance, what if Merlin had revealed his magic during the battle against Morgana in a certain episode? These types of fanfictions add a new twist to the story. Also, there are fanfictions that center around Merlin's family. Maybe his mother comes to Camelot and how that changes the dynamics. They often provide a deeper look into the character's background and motivations.
You can try some of the major fanfiction websites like Archive of Our Own (AO3). It has a vast collection of Merlin fanfiction, and you can easily filter by the publication date to find the older ones. Another option is Fanfiction.net, which has been around for a long time and has a good number of old Merlin fanfiction stories as well.
One possibility is that there would be a great deal of tension. Old Merlin has seen so much and has his own wisdom, while Morgana has her own powers and motives. Maybe Merlin would try to persuade Morgana to abandon her dark path. He could use his experience and the bond they once had to appeal to her better nature.
Previously, their interactions were sometimes clouded by Morgana's gradual descent into darkness. Now, old Merlin meeting her could be a moment of reckoning. He has seen the full consequences of her actions over the years. This encounter would likely be more intense, as Merlin might try to make Morgana face the truth about the harm she has caused, which was not as clear in their earlier interactions.
In a more humorous take on the 'Merlin tied to a bed' fanfiction, it could be that Merlin has fallen ill and the overly - protective Gaius has tied him to the bed to make sure he rests. Merlin, being the active person he is, complains constantly. Arthur comes to visit and teases Merlin about finally being still for once. Meanwhile, Merlin tries to convince Arthur to let him loose, promising that he'll be fine. Eventually, Gaius relents and unties Merlin, who then immediately starts bustling around the room.
If Merlin died in the fanfiction, it could trigger a series of tragic events. The balance of power could tip, and the villains might seize the opportunity to attack. It could also bring out hidden strengths in the remaining characters as they try to cope with the loss.
One more idea is that Merlin is tied to the bed in a dream - like state created by an ancient magic. In this dream world, he is faced with his deepest fears and insecurities. His friends in the real world notice his strange behavior and try to wake him up. Merlin, while in the dream, has to find the source of the magic that is binding him and break free. Through his inner strength and the memories of his friends, he manages to do so and wakes up, having learned more about himself and his magic.
If Merlin is a Dark Lord in fanfiction, it could be an interesting exploration of the 'nature vs. nurture' concept. Maybe he turned dark because of the constant fear of being discovered and persecuted for his magic. His actions as a Dark Lord might include taking over Camelot or exacting revenge on those who wronged him in the past. It gives a whole new perspective on his character.
Well, in such a fanfiction, there could be a lot of self - discovery. Maybe the old Merlin gives advice to his younger self. For example, he could tell the younger Merlin about future challenges and how to avoid some big mistakes.