This is days late so I'm just tossing it at you. I'll at least run it through Grammarly before the Ao3 post though.
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There’s something off about Arthur’s room. That’s the only way to describe it. He’s not sure what, though, and Merlin cleans it regularly. All his clothes are in the waredrobe. No has has stolen his crown. Or even his boots. But still, there’s something different about it and it’s puttle Merlin on edge.
He pauses in his efforts ot make Arthur’s bed, gazing over the floor, at the hearth, into the corners and…there.
There’s an odd dark spot in a corner. There shouldn’t be, there’s not an extra crevice. The shadow should be the same color all the way through.
Merlin blinks, and the shadow is all the same color.
He shakes his head. Of course the shadow is all the same shade of black. That is normal. There is no reason for it to be two colors. But even as he things that, he notices one of the shadows cast by the chairs are darker than the others.
He squints at the shadow, which moves and Merlin knows instantly it’s not actually a shadow.
It stretches quickly across the floor, reaching for Merlin’s feet and he knows he can’t let it touch his own shadow. Merlin scarmbles backward, hitting the edge of Arthur’s bed and rolling back on to it, pulling up his feet just before the shadow touches him.
He freezes.
Nothing moves in the room. No shadow. No creak of the bed. It’s got to be under the bedframe, whatever it is, and now that Merlin knows it can move independently he realizes he’s trapped himself. As soon as Merlin gets off the bed. As soon as he casts a shadow on the floor, it’ll touch him and…and do what, he’s not sure.
But he can’t leave. Not until he catches it.
How do you catch a shadow?
Merlin looks toward the window. The days are getting shorter, and the sun sets around the time Arthur has supper. Sun set brings longs shadows and Arthur, a situation he doesn’t want to be in. He’s got an hour maybe to figure out how to catch this.
You can’t really catch a shadow, it just moves and shifts as the light moves. Even if you shine a light directly over something, there’s a shadow underneath. Merlin can’t be dealing with an actual shadow, and it acts independently of light sources. It had flowed and moved, and Merlin had sensed it so there’s got to be a presence there. Some type of magic that fizzled against his own. Some type of awareness, to know it had been recognized and launch an attack. It’s got to have a body, and a body can be trapped.
But a small body, and something fluid that can stretch and flatten. He’s not looking to trap a shadow, he’s looking to trap a sentient cup of water.
Normally, he’d just grab a rag and mop it up, which he doesn’t think will work here. But if he can use to his magic to create a cup, force the shadow into it....
He looks down at the stone floor. He can’t get off the bed, his shadow would be a target. A quick glance around the room confirms the shadow hasn’t left the space under the bed, and Merlin grins. What he thought was a trap for himself, is now a trap for this creature.
He’s still new a shields – normally he just makes physical barriers stronger – but now he whispers under his breath and casts his magic down. It fills the gap between the base board and the floor on all four sides of the bed. Then, he encourages his magic to spread, cutting across to form a layer under the bed and over a floor to create a box.
The shadow creature seems to know immediately what Merlin’s doing, but his magic is fast. While the shadow throws itself at a corner of the barrier, Merlin completes his golden box and starts shrinking it from the headboard.
The shadow goes liquid, spreading flat and prodding all over for a weakness. It makes Merlin shiver, it feels like leech slime spreading all over his body, and he grits his teeth. If this is what it felt like, contact between his magic and this creature, Merlin doesn't want to think about how it would have felt if it connected with his shadow.
Merlin condenses his box faster; it is half the length of the bed now and the shadow is pushing against all four corners. The pressure bounces back to Merlin, so it feels like the shadow is pressing against his skin. The more he shrinks the box, the more the pressure gets. It’s a miracle he doesn’t see divots in his forearms from the sensation of someone pushing and pushing.
Whatever this thing is, it’s magic and is able to work through the link Merlin has to his own. Once he traps the shadow, he cannot keep it trapped. He’ll need to find some other prison for it.
Merlin mimes folding sheets, and with each motion the box under the bed gets smaller. An inch from the left, an inch from the top. As the box gets smaller, the pressure on Merlin’s body increases. It feels like there’s a corset around his ribs. A tourniquet around his calves. He tries not to whimper as the pressure turns to pain, panting as he forces the box smaller. It’s hard, there’s so little space not filled with the shadow-creature, and he’s reaching the point where it can barely compress itself further to avoid the narrowing space.
Something in his hands grind, and he wonders if he’s fractured a finger. Is the pain and pressure actually something happening to his body, or just a magical sensation from the shadow trying to figure away out. He doesn’t know, but he’ll be talking to Gaius after this.
Merlin pants for a moment once he can’t compress his magic cage further, then tips over the side of the bed to look underneath. There’s a small, glowing box under the mattress. It’s barely bigger than plate – wide but flat – and Merlin things he could wrap it in a dirty shirt and carry it under his jacket. He doesn’t want to actually touch it with his skin.
He flops back against Arthur’s bed and breathes. The pressure on his body is there, fierce and insistant, and Merlin knows it won’t go away until his magic stops restraining the shadow creature. But right now, he can’t stomach the thought of moving. Of rolling off the bed, walking through the castle, and finding a metal cage.
It needs to be done, but every bone in his body protests. He holds back a whimper.
No one else can get rid of the shadow, and he has maybe fifteen minutes he guesses, by the angle of the sun, to leave before Arthur returns. He needs to get up. He had things to do.
But the shadow isn’t even pushing aggressively against the wall, it’s just squeezed in so tightly. Merlin wonders if so much pressure on his elbow will pop a joint.
He manages to get off the bed and pick up the boxed shadow before Arthur shows up. He does a double take upon noticing the thing of magic in Merlin’s hands, reaching toward his sword.
“Merlin, drop that.”
“It needs to be locked up. If you find a place, I’ll drop it in.”
His words are wooden, Merlin knows, because there are a hundred fingers pressing into his skull just as a hundred more press into his jaw. He doesn’t want to move and talking is a type of moving.
Arthur’s gaze darts ot the magic box. It’s gold and shimmery. Obviously magic. Merlin hopes Arthur doesn’t ask questions. Like, who made it.
But there’s enough trust between them that Arthur starts to consider the objects in the room.
“Any place?”
“Completely sealed. No cracks. Probably best if there’s limited seams too.”
A vase, made from a single lump of clar. A cast iron box, formed by a mold.
Arthur holds out a small, glass bottle. It’d work but: “To small. Twice that size at least.”
Arthur frowns as he thinks. “Would welded seams work?”
Merlin nods. He don’t want to open his mouth. Arthur seems to pick up on something wrong, because he doesn’t say anything and rushes out the door. Merlin falls to the floor, not even bothering to move to a chair. He doesn’t want to move.
Minutes later, Arthur comes back in with Morgana hot on his heels. “You can’t just steal my jewerly box, Arth-Merlin!”
She rushes to his side and briefly touches his cheek. Merlin barely feels it, the way the shadow pushes on the skin, echoed to his body, too intense for him to pick out human touch. He blinks at her.
“He said we have to drop in that into a sealed container. Your box is roughly the same size but with welded edges so it can’t escape.”
“What about the lid, moron?”
“We’ll get Gwen’s dad to close it!”
“It’d probably get out first.”
“I’ll weld it,” Merlin grits out. His secret is half way out already, and if he reveals it to the both of them he’s fairly sure Morgana would give him the time to run.
“Since when are you a metalsmith, Merlin?”
Merlin glares.
Morgana yanks the jewerly box out of Arthur’s hands. It’s already empty of adornments, and there’s a few partishions. The top is raised, so the shadow will have a little more room than Merlin’s magic box. Either way, he’ll have to act fact.
He locks eyes with Morgana, who hasn’t batted an eye at Merlin’s magic trap, so maybe he should have ignored all the advice he’d gotten about not reaching out to her. Regardless, they work seamlessly. She flips open the lid, Merlin shoves his little box inside, wraping the dimensions to fit. It hurts, and when he sways Arthur catches his side. Then, Morgana slams the lid shut and Merling makes no attempt to hide the spell he mutters. He runs a finger along the lid’s seam, melting metal, as Morgana rotates the box. Only when he’s done does he release the shadow from it’s prison.
The sudden release of pressure from his sink feels like he’s lost fifty pounds. He takes a deep breath and coughs on the empty air, curling over his knees. The sense of Arthur by his side has disappeared.
When he looks up, it’s to see Morgana’s glowing, curious face. “You’re a sorcerer,” she whispers.
Merlin nods.
She looks toward Arthur, then returns her attention to Merlin. “I think I’m a sorceress.”
“I think you are too,” Merlin whispers back.
“Nope!” Arthur pushes himself to his feet and starts pacing the room. “Nope! I did not hear that.”
“What was that?” Morgana says. Her voice is still soft and excited. Merlin doesn’t know what she’d talking about – the shadow, his magic trap, or his finger welding.
It doesn’t matter. While the pain is gone, there’s the memory of it still lingering on his bones. Not that long ago, it hurt to move, and while he can now all Merlin wants is to rest.
“Help me up?”
Morgana hurries to obey and Merlin wobbles when he’s on his feet. Arthur watches them, eyes dark, but his sword is on the table now and Morgana’s body is in front of his.
“Take him to Gaius’s,” Arthur commands. “He’s dead on his feet. But you, both of you, are to break your fast with me and answer a lot of questions.”
“Of course,” Merlin says, grin splitting his face.
Morgana will probably get in a few questions first on the walk through the castle, but that was fine. Merlin scooped up the jewerly box and let her lead him out.
