Merlin Headcanons

Once, Present, Future

Merlin isn't mine. Nor is anything else you recognize.

Kilgharrah said Arthur was the Once and Future King. He says this throughout the show.

But if you think about it for a moment, this doesn't actually make sense.
Now, if Merlin, after Arthur's death was to say this, it would. Arthur used to be king, and, someday, he would be again. Once. Future. Done.
But Kilgharrah first said this back when Arthur was still a prince. How could he be a 'Once' king, if he wasn't even king yet in the first place? He continues to call Arthur this once he becomes king, but again, his reign should be present tense, not past.
What if . . . What if Arthur was actually destined to be king three times? What if he was called this in the fifth season because he had 'once', hundreds of years ago, been king, was currently king, and would be king in the future?
If that were the case, then who was Arthur's previous incarnation?
Arthur's destiny, we're told, is to unite the land of Albion and return magic to the land. Set aside the magic for the moment. Who do we know who fulfilled the first half of that destiny?
King Brutë, that's who. The man who turned a bunch of squabbling tribes into a kingdom. One of Arthur's ancestors. And probably a member of that original Round Table that Arthur, despite having a bad knowledge of history, recognized immediately and respected.
What of Merlin? Was he in Arthur's previous life?
Maybe. After all, Arthur noticed "something" about him. Maybe he sensed the magic, or the destiny, or just the insolence.
Or maybe he recognized him.
This would be somewhat depressing, as it would indicated that he wouldn't remember Merlin in his next life. However, we actually don't know that he had forgotten. Merlin's not the only one who can keep secrets, after all.
But perhaps Merlin wasn't in his past life. Either way, this brings me to my next point: magic. Because, in a strange way, Arthur did return magic to Albion.
Merlin is "magic itself", after all, and besides even him, magical attacks really seemed to pick up around Arthur's twentieth birthday.
Granted, that's not what Merlin and Kilgharrah had in mind. But let's face facts: magic didn't actually need to be returned to Camelot. Legalized, yes, but that's not what the prophecy says. It says returned, despite the fact the magic hadn't seemed to have left.
In other words, this seems more a job for a future Arthur, one who returns to find Albion truly bereft of magic. This would only happen if Merlin had left, so let's assume the memories got to be too much and he moved elsewhere. America, Australia, doesn't matter. Arthur would have to go and get him back, returning magic, and perhaps reviving some of those creatures of the old religion in the process. After all, doesn't anyone find it odd that all the magical threats seemed to wait to attack until after Merlin came to Camelot? Destiny? Or were they drawn to his magic?
So if Brutë united the kingdom and future Arthur (let's call him Bradley) is going to return magic, than all Arthur would have to do would be to cultivate friendships and loyalties so that he'd have people to help him in his final life, something, on the whole, he did well.
Just a thought.