Another possibility is that the cat is actually a transformed being. It could be a person who was cursed and Merlin has to find a way to break the curse. The cat could communicate with Merlin in a special way, like through dreams or by leaving paw prints that form messages.
Perhaps the cat is a familiar sent by an old wizard to help Merlin in a difficult time. It could protect Merlin from danger, like warning him of approaching enemies or using its own small magic to create distractions when Merlin is in a tight spot.
The cat could have a special bond with Arthur too. Maybe it likes to curl up on Arthur's lap when he's in a pensive mood, and this makes Arthur more open - minded about magic. The cat could also be involved in a situation where Arthur has to rely on Merlin's magic, which the cat is somehow connected to, to save his life.
One idea could be that Merlin and Elizabeth go back in time to Camelot's golden age. They could use their modern knowledge to solve ancient problems. For example, they might introduce new medical techniques that save lives. Another plot could involve them trying to prevent a major disaster in Camelot's past that they know about from history books. They might also have to deal with the cultural shock of living in a different time period.
Perhaps a story where Tiny Merlin accidentally shrinks the whole Camelot and has to figure out how to reverse the spell. He would have to use his wits and small - size advantages to solve the problem. This could involve sneaking into small spaces in the shrunken Camelot to find the source of the spell. It would be a really fun and adventurous story.
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 uses his magic to help Sherlock solve a case that seems to have supernatural elements. For example, a series of murders where the victims all seem to have died from some unexplainable force. Merlin's ability to sense magic and his knowledge of the old ways could give Sherlock new perspectives on the case.
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 that Merlin uses his magic to help the Avengers in a battle against a powerful magical enemy. Maybe he disguises himself as a normal human at first and then reveals his true powers when the situation is dire.
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.