Well, an interesting plot idea could involve Merlin meeting other dragonlords from different lands. He might have to team up with them to defeat a common enemy that threatens all magic - users. Also, a plot where Merlin loses his dragonlord powers temporarily and has to find a way to regain them while still protecting Camelot would be engaging. Additionally, a story where the dragons start to lose their magic due to a curse, and Merlin has to find a way to break it could be really cool.
It could be about Merlin's discovery of his role as the Dragonlord in a more in - depth and unique way related to EEG. Maybe EEG is some kind of magical energy or a special ability in this fanfiction. For example, Merlin might use his connection to the dragons, which is enhanced by EEG, to defeat a new and powerful enemy that has emerged in Camelot.
Perhaps the OC Dragonlord is a bastard of a Targaryen. They grow up in Essos, learning the ways of dragon - taming from an old sorcerer. When they hear of the chaos in Westeros, they decide to cross the Narrow Sea with their dragon, planning to claim a throne for themselves. Along the way, they form an unlikely alliance with a group of outcasts, who help them navigate the political intrigues of Westeros.
One interesting plotline could be Arthur's initial shock and then his gradual acceptance of Merlin's new identity. He might start to see Merlin in a whole new light and realize how much power Merlin truly holds.
Power and responsibility is a very common theme. As a dragonlord, Merlin has great power, and fanfictions often explore how he deals with the responsibility that comes with it.
To write a good character in Merlin the Last Dragonlord fanfiction, first, give them a distinct personality. For example, if it's a new wizard, they could be really shy but super powerful when it comes to fire magic. Second, give them a backstory that ties into the world of Merlin. Maybe they were an apprentice to a wizard who was killed by Morgana. Third, make their actions and decisions drive the plot. If they choose to side with Merlin, it should have consequences for the story, like making them a target for Morgana's wrath.
One plot idea could be Merlin and Nimue teaming up to save a magical forest that is being threatened by dark forces. They could use their combined magic to fend off the evil entities. Another idea is a time - travel plot where they are sent to the future and have to adapt to the new world while also finding a way back. And perhaps a plot where they are wrongly accused of a crime in Camelot and have to prove their innocence together.
One idea could be Merlin having to deal with the political intrigue of being a king. He might face challenges from nobles who don't trust his magic. Another could be Merlin using his magic in unique ways to improve the kingdom, like creating new irrigation systems for farmers. Or perhaps he has to form alliances with other kingdoms while hiding his true identity as a powerful sorcerer.
One idea could be that Merlin, as a wizard, is hunted by vampires because his magic is seen as a threat to their existence. But then he discovers that some vampires are not as evil as he thought and they form an uneasy alliance to fight a common enemy, like a dark sorcerer.
One idea could be exploring a different magical realm within the 'the merlin conspiracy' universe. Maybe there's a hidden land where the magic is more primal and ancient. Another could be a story about a young wizard who discovers they have a unique connection to Merlin himself and must use that to stop a new dark threat.
A plot could involve Merlin getting cursed and the knights having to find a way to break it without Merlin's magic to guide them. They might have to rely on old legends and their own wits to save him. This could lead to some great character development for the knights as they face challenges they usually rely on Merlin to solve.