He breaks the contact and waits for Arthur to make the next move.
Arthur takes a deep breath and tilts his head slightly and still Merlin waits, to see what comes next, but the other man isn't moving. And then he realises that whilst he's waiting for Arthur, Arthur is waiting for him, because the next move was all his and he knew it would set the standard for the rest of their lives, however long and entwined they might end up being.
So Merlin pushes forward and kisses him, a teasing press of lips and then he reaches up and takes Arthur's face in his hands, and he knows his hands are trembling but it doesn't matter, because so are Arthur's lips and that's fine. He takes the time to look, to really look at Arthur – the way his left eye is slightly wonky, the small scar just under his bottom lip, the few freckles scattered over his cheekbones. Imperfections, yes, but they're a part of him and so by extension a part of Merlin too.
Arthur surges forward out of his grip and his hands fall to the Prince's shoulders as he pushes against him, mouth hot and open on his and this is different, but this is Arthur, so different is fine.
He knows that they're moving, feels his feet shifting along the floor even as Arthur's tongue presses against his, but it's gentle. They're moving slowly as though through water and besides, Arthur's hand is on his back and on his neck and guiding him; he knows that they've ended up outside because there's a sudden breeze, not cold at all but quite pleasant, and some part of his mind registers that he's never been on Arthur's balcony before as he twists his fingers in the blond hair.
Arthur's fingers slip under his shirt, brushing the sensitive skin just between his hip and his stomach and Merlin jerks away instinctively, then immediately pushes back into the touch, warm and welcome and comfortably unfamiliar. Arthur's hand catches, drawing the cloth up towards his chest and Merlin doesn't think, just helps it along, aware that he'll probably get cold if he's going to start taking his clothes off outside, but as the shirt is thrown to the side he realises it doesn't matter because Arthur's pressing up against him, and he's warm enough for both of them.
Merlin's hands still aren't steady as he moves, taking the hem of Arthur's tunic and the material is soft in his hands, as soft as the Prince's skin and hair, as he pulls it over and off and discards it and now they're equal again, skin bare and glowing in the gentle torchlight reaching them from the Prince's chambers.
Arthur seems to hesitate, but Merlin realises that he's not – he's just looking again, gazing at the warlock with something lurking in his eyes that Merlin doesn't recognise and can't defend himself against. But then Arthur's pulling Merlin against himself, hips and knees and shoulders and collarbones bumping as he wraps his arms fully around him, lips pressing briefly to Merlin's bare shoulder and the moon eases out from behind a cloud.
Merlin can hear an owl hooting as Arthur's hands trace indistinguishable patterns on his back and he pulls back slightly, a warm breeze brushing his cheeks, and he thinks he can see the stars twinkling and reflected in the other man's eyes (or maybe they're just in his eyes), and kisses him softly before leaning forward again to rest his chin on the other man's shoulder.
Cheek to cheek and skin to skin, Merlin can feel Arthur's breath grazing his neck as he squeezes shut his eyes, concentrating on breathing in, out, in, out, and not forgetting to stop. This time, their chests are pressed together and this time they're moving together, which is how it's meant to be but not with Arthur; they've always been at odds and this should be no exception.
And then Arthur's hands are moving again, his whole body's moving and Merlin realises that he's toppling over a bit too late – but he's not falling at all, and even if he is, he's not falling alone, Arthur is falling with him. And when he hits the floor it's not hard, not like he expected, but a part of him is expecting it when he feels Arthur's hands slide between them. He knows what's coming next, and thinks that the dragon probably does too. Because he is falling – with him, and for him.
It's becoming clear to him that he's not paying enough attention because his trousers are around his knees and so are Arthur's and he hasn't noticed any of it, and then they're completely gone from both of them, and this should feel strange but it doesn't. It feels right.
He has no idea what he's doing but he knows that Arthur's in the same boat as his hands grip Merlin's hips for a second before twitching and releasing and pressing against his ribs, thumbs digging in just a bit too hard. He's looming above him and the moonlight is shining over his head like some sort of halo, and Merlin stretches his neck to kiss him again, hand reaching up to pull Arthur down and closer to the ground.
And then Arthur's hips are between his and his hands between them again, and Merlin's eyes roll slightly as his head lolls back and hits the floor with a painful thud. And in a heartbeat one of Arthur's hands is there, cradling his head and pressing his lips to the warlock's temple then his eyelid, cheekbone, corner of his mouth.
Arthur's other hand is warm and deft and gentle on him as he pushes Merlin's legs apart and he looks straight into the warlock's eyes with something startlingly tender as he presses into him, and then Merlin has to look away because it's both wrong and right at the same time. But he's moving with Arthur anyway, stone floor rough and cold on his back and the other man's skin warm and soft all over him, and he has enough of his wits left to take the Prince's face and hold it steady as he kisses him and it's clumsy, it's awkward – it's an unfortunate collision of teeth and lips and tongues but neither of them mind, and Arthur may be smiling. A clatter of pots travels up from the kitchens far below.
There's something clean and sharp about Arthur even in this state that Merlin can't even begin to describe – but for the first time, he's not controlled, and it's obvious because his left leg is trembling and his movements are erratic, an uneven rhythm that Merlin's trying to match and failing. So he stops trying and makes his own, pressing back as he thinks he hears his name on someone else's lips and then something just cracks.
His hands are splayed over Arthur's spine as his eyes roll back and he sees white and gold and black, and perhaps he passes out for a few seconds because he's aware of an immense feeling of contentment rolling through him, and then his right side chills slightly. He forces his eyes open and notes that Arthur has rolled off him and to his side, hand resting almost tentatively on Merlin's chest.
Merlin turns to the side and looks at Arthur, whose forehead is coated with a faint sheen and whose face is flushed, and whose shoulders are shaking. He pushes forward and kisses him, not entirely sure who he's reassuring.
There's a deep thrumming of magic in his bones now, strong and insistent and he knows that his eyes are glowing but he doesn't even try to stop it, because Arthur's not looking – the Prince's eyes are half-shut and they're staring somewhere beyond him, into the night sky. He thinks his whole body might be glowing. It doesn't bother him.
They are as silent as the night air around them, and Merlin is at peace.
He thinks Arthur probably is, too.