Future Magic-Slavery AU
I have this freaking awesome idea at one point that was like a future magical AU. Each sorcerer is magically bound to a nobleman and is forced to obey their commands. There’s like a collar brand of some sort and if a direct command is disobeyed, then it causes a great deal of pain until the command is fulfilled, like electric shocks or something. If one continues to resist the command, the shocks will eventually become lethal.
To do this on purpose is to commit suicide by disobedience.
So starts out that Tom Collins, who was Arthur’s bound sorcerer, tried to kill Arthur because Tom’s mother was old and feeble and physically incapable and completing the task her master set her and was killed by her bond. So Arthur needs a new sorcerer. Merlin had been bound to Will, but Will was such a rebel that he refused to give Merlin any commands at all and gave him as much freedom as he possibly could and treated him like anyone else. But then some douchebags (maybe Valient and Dagr or someone) took offense to how lenient Will was and attacked them both. The only order Will ever gave Merlin was to save himself, but Merlin interpreted it as an order to save them both. He couldn’t manage to save Will, though, and Will died. It was just his word against the assailants, and they both insisted that Will had ordered Merlin to attack them and they had reacted in self defense. And the word of a sorcerer slave means nothing.
Merlin is reassigned and bound to Arthur. Merlin is obviously ridiculously outspoken for a bound sorcerer and opens Arthur’s eyes to a lot of things by doing stuff like, for one, speaking out frankly and, for another, waiting as long as he can possibly stand to fulfill an order so that Arthur can see how much it hurts him to disobey, even for small commands like fetching something from across the room. When Arthur sees how excruciating the bond is for Merlin, and because Merlin is acting like a person with a personality instead of a obedient magical slave, he starts finding it hard to justify subjugating people like him for the mere fact that they have magic. He starts questioning everything his father has told him about sorcerers and how they need to be bound because they're evil and cruel and violence when they're uncontrolled.
I had more to the story at one point. Something about Morgana developing her powers late and never being tested, so she’s unbound. Morgana working with her bound sorcerers Morgause on a way to break the binding. Nimueh was Uther’s bound sorceress and was secretly trying to kill him, I think. Morgana tagged Merlin to bring him into the plan but Merlin was already trusting Arthur by then because it was clear that Arthur was coming around. He was treating Merlin more conscientiously and being more careful about his phrasing so he didn't accidentally say something that could be interpreted by the bond as a direct order when he didn't mean for it to be and phrasing things as questions more often so Merlin has the option of not obeying or at least questioning the order.
I had a romance scene where Arthur wanted to kiss Merlin but Merlin resisted very strongly because Freya committed suicide by disobedience after years of sexual abuse by her master. But Arthur swore on his honor that he would never command anything like that from Merlin, no matter what, and he would never bring it up again if Merlin would just give him one kiss of his own will. Idk, it was just a really cool universe to play around in.