A/N: Response to a prompt on the LJ Community kinkme_merlin.
"Oh, for god's sake, Arthur, it was harmless flirting," Merlin said, exasperated, as Arthur dragged him back to their chambers. Arthur's possessiveness was endearing, most of the time, but in moments like right now, it was just irritating.
"It stopped being harmless when she kissed you, right there, in the middle of the dance floor!" Arthur growled. "She should know better than to do that with the King Consort-"
"Yes, well, it's not exactly official, is it?" Merlin asked.
"How is it not official?"
Merlin laughed. "I've been in court intrigue long enough to know that she could claim lack of knowledge of such, considering you never gave an official announcement. Even if we have been rather lacking in discretion for half a decade."
They'd stopped in the hallway, Arthur still clutching tightly to Merlin's wrist. He turned around and brought his other hand up to the nape of Merlin's neck, bringing him in for a claiming kiss.
"You are mine," he hissed. "And I will prove it."
Two days later, he did.
Merlin was rather amused by the official decree of his being the King Consort. Mostly confusion, as pretty much everyone found it rather redundant. Everyone had already been calling him 'King Consort Merlin Emrys, Court Sorcerer for Camelot' for quite a while.
The way Arthur claimed Merlin for himself that night, however, was much more fun for Merlin - making this entire debacle worth it.
Arthur smirked as he finishes tying the last knot, leaning back to drink in the sight of Merlin tied, eagle-spread, to the bed-posts, smiling congenially, and awaiting whatever it was that Arthur had planned.
He seemed rather confused by the placement of a knife in the fire, especially as there was already one on the beside table, but he went along with it just fine, like always.
Arthur slowly picked up the knife, and without hesitation, laid the knife to Merlin's chest, just below where it met with his neck.
"As I said," Arthur said as he pressed down on the sharpened blade, making Merlin hiss. "You...are...mine."
Merlin nodded weakly, caught up in the painful-pleasure, as Arthur carved his chosen sign into Merlin's very skin. It was an ornate A, but oddly deep - a bit more so than Merlin was used to for their games.
Whatever Arthur was playing, Merlin would keep up.
Merlin was breathing heavily, Arthur's rhythm matching from his kneeling position by his side, when Merlin asked, "Is that all you've got?"
"Not at all," Arthur said, getting up and walking over to the fireplace.
Merlin's eyes widened in realization as Arthur walked back with the glowing hot knife.
"What are you-"
"Cauterizing the wounds, of course," Arthur said, as if it were obvious, despite the fact these cuts most definitely didn't need it.
Arthur swung his leg over Merlin's hips, straddling the warlock, and smirked at Merlin's wide-eyed silence, before pressing the glowing tip to the tip of the bleeding letter before him.
Merlin screamed as he arched into the air, and writhed, bound in the ropes, as Arthur dragged the glowing-hot knife down.
Merlin fell flat and still against the bed when the knife was pulled away, breathing heavy and ragged, mouth opened partially to draw in big ones, lips forming an almost oval.
He screamed again, the second time the knife came down.
On and on this went, Merlin screaming with Arthur burning, but both their hard-ons got stiffer and stiffer, until all of Merlin's wounds were black, by which time the ragged panting had gone from pain to pleasure, and Arthur brought them off with a few tugs each.
Dropping the knife to the floor - it was pretty cool, now, anyway - Arthur collapsed by Merlin's side, without bothering to untie him, and wrapped his arms around the pliant, sleepily-submissive man and rested his head against Merlin's chest.
"Mine," Arthur growled again, and Merlin couldn't agree more.
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