If he thinks about it, Merlin can remember no moment in his life where Arthur's voice wasn't there: it has always been inside his head, long before they first met, the sound of his own soul intertwined with his king's. It was the voice, not the looks that made him stop that first day, countless years ago and watch. It was the voice that rang through his ears while his own brain silenced in the face of golden beauty that had led him to throw a punch. In the rush of both their hearts as their bodies aligned, Merlin's back turned towards Arthur's front, it brought an explosion of sounds from inside and outside that sounded the same as only soul mates can.
He doesn't remember his own voice anymore. Every time he speaks up, it sounds foreigner to his own still oversized ears because… He never hears it, not inside his head. He can't even think with his own voice, it is as if this part of him had gone to rest along the best part of his soul. All he hear is Arthur.
Merlin can barely remember his face, only golden hair and blue eyes. A thousand years gone by, so many people he has seen, and even if none of them were nearly as important as Arthur, everything tends to fade.
But his voice doesn't – it still sounds inside his head, putting his thoughts into words and criticizing everything he does. Arthur in his head tells him to live, but he does not have the strength for it, or the courage. All he has is the magic he is, bearing him through centuries of loneliness and waiting.
Sometimes he forces his ideas to become words, only to listen to Arthur's voice. He tries to think of his own name often – not Emrys, as some called him, and not Ambrosius as other people did, but Merlin – just Merlin. He can hear the thousand different ways his king said his name and all the emotions underneath it, all the affection he had been blind to when he was alive.
He had been blinded by lots of him when Arthur was around – the brightness of his presence made everything else fade into obscurity; even his own feelings. How could he not have known that he belonged to Arthur, body, heart and soul until he was almost lost? How could he not know what he truly wanted until Arthur was pulling him down and he was resisting, not wanting to do it when he had failed? How could he not hear the love in the words that wished him to be nothing but himself?
All the years of his youth, he had heard that they shared a destiny, but only in the ages after it was gone he finally understood what it meant: to be bonded through their own souls; forever linked, symbiotic. He knew Arthur would return because he was still there; he could hear his voice and the faint beating of his healing heart far away in the middle of his own. The world had parted their bodies, but they still sounded inside each other, and he wondered if in his dreams, Arthur too heard him – probably he did.
He waits in silence, but the silence is company: the voice of Arthur in his thoughts and the beat of his heart in Merlin's chest. It is not lonely, it is as close to whole as he can be. And he waits, in silence, for the sounds to rush into one once again, their bodies aligned, facing each other this time around and uniting as only soul mates can.