He never stops yelling.
He always expected hell would be fire and chains, something physical that he could fight against. There's honour in the pain sustained in battle, and he always thought that if he found himself in the worst of all nightmares, by whatever evil or sorcery, that he could strike out against it with or without his sword. That the Great Prince Arthur would never go down without a fight, no matter how hopeless the scene.
This, though. This is --
His body is a foreign object, his hands and lips and voice still all his own but he has no control, no power over any of it. He tries to look away, maybe break the hold over him even for a fraction of a second, but he can't even blink on command. He feels drunk without the buzz that makes everything alright, like too much bad ale but he can still see so clearly. He feels possessed, a distant viewer to his own life, but there's no connection and his sword lies uselessly on the shelf, his hands stay open and vulnerable. He screams and shouts and begs, and his body wilfully ignores him.
This is true hell, and he's trapped.
Merlin confronts his other self (so much responsibility on those shoulders, and for once, just this once, he denies it all) as his hands are packing and he finds enough power for long enough to make a fist; he lets the anger and the hate burn through him until drumming fills his head and he can't even hear what his lips are saying. He can't stop the way Merlin looks at him, and it just makes it burn harder. (he must know it's not me, he must--)
When this spell is broken, he promises himself. I'll make it right.
There is a tug when he first meets her, a sense of something not -- but it fades as his lips touch her hand and her eyes dance. She's beautiful, he thinks, and leaves it at that.
He has this need to be near her, a conflict of what's acceptable and what he wants, but Merlin makes it easy to choose (he doesn't need anyone else's permission, but there’s a reason why Merlin gets away with so much) and it's so natural to ask for his help. Too easy, perhaps, and maybe he should consider that sometime but then Sophia catches his eye across the dining hall and smiles, and he forgets everything but her.
By the time she catches him in the woods and starts to murmur soft, strange words for the first time he's too far gone, too much in love, to realise that his fingers should be on the hilt of his sword. But still, there's --
There's something wrong with the way he can't stop looking at her, the way his whole body lights up at her touch. There's nothing he can compare it to (except, perhaps -- no, nothing) and so he just assumes that's how it's meant to feel, that this is the way Love works like it's told in old stories, grand and powerful. It scares him, just a little, but there's no one he can admit that to.
She takes his hand and he takes a step back into his mind. There was a moment -- just a moment -- when he questioned it, but skin on skin and the world slips sideways. His eyes turn red, and he starts screaming without moving his lips.
Uther laughs. If he had any control over his arm right now, even the smallest scrap of power, he would have punched him just to make him see how wrong things were, how this is clearly not him.
He's a joke, and he's going to kill Sophia the moment he gets free. Is set free. Whatever.
He's known the truth since that vile whore pushed herself on him (how did he ever think she was beautiful?) but to hear it out loud, to hear Merlin say it all, makes something shift a little, break apart. It gives him enough control to turn away from them both, feeling suddenly intensely sick and dizzy but at least it isn't the empty numbness that had filled him so wholly. His vision swims and he fights, he's going to break this, it doesn't matter what they try to make him do or say because he can get out of --
His eyes watch as Merlin is thrown against the wall, and he screams louder but it feels hollow. Desperate, and hopeless.
Every step hurts. He knows he's going to die at the end of this and maybe there's nothing he can do, but he resists every step and feels every inch of him burn and he doesn't stop walking and he doesn't stop trying. If he falters, it's only ever for an instant then he's taking the next step, eyes glowing.
He's a puppet by the end, still shouting for help but it's getting quieter by the second. His vision blurs a little and his boots flood, the freezing water rushing to his skin but it's already feeling a little distant, numb. There's nothing he can do. Trapped, and helpless.
His lungs fill with water.
(There are whispers when he awakes, the ghost of hands holding him, a breath of unbreakable security. It flickers a little harder when Merlin grins at him, wide and careless, and Arthur wonders just how big that lump of wood was.)