This story is cross-posted from ao3 under the name fooma_foolish_mortal in case you're interested :)
Deep below the waves, resting on the sandy sea floor, a creature of darkness lingered outside of his murky, deep dwelling. He was sent into the abyss of the darkest trench where no light had ever reached to collect information. And with that information he was tasked to keep order among the diverse sea dwellers. He had no time for trivial distractions and he had no need for companionship or light. He had not seen a hint of light (no sun, no stars, no moon and it ached deep inside his chest) in longer than one can comprehend and he had almost forgotten the warm tingling it brought beneath his skin (he had scales now anyways) and he could no longer recall exactly what made him yearn so painfully for the scent of salty air and sunshine (sometimes he heard the phantom whisper of 'darling' in his ear, but that couldn't be right. He no longer had those types of ears). Sometimes he had distant dreams of himself in a different form with a creature of light that could shift into anything and loved to tease him. But these dreams were easily dismissed. He had no time for whimsical dreams of a time long passed (did it happen at all?). He was Arthur, and he had a job to do.
He didn't know what to think when the swirling, dim moonlight made its way to him. It was clearly being manipulated by a creature of light. Usually Arthur would be cautious, but it had been so long, and he could taste the light in a way that felt almost familiar (I won't forget you, love, don't be so dramatic) and it almost made Arthur want to cry. The slip of silver weaved its way towards him and wrapped itself around Arthur's muzzle, and Arthur felt like he was home. But he didn't have time for these distractions, because he had been sent here for a purpose (who had sent him here and torn him away from his other half?). So Arthur ignored the beam of silver and continued to gather information and keep control of his dominion.
When it happened again, it was a beam of the brightest yellow. It had the same taste of forgotten dreams and safety lost to the above that the moonlight had had. Arthur spent longer looking at it this time (sometimes I can get the color to travel with the light, darling, isn't it beautiful?). Suddenly, he didn't want to be in the darkest, deepest, pit the sea had to offer. He wanted to see the surface, and he wanted to see the creature of light that left such a feeling of longing and regret throbbing in his heart. He needed, but he had a job to do. So Arthur let the bright yellow tendril weave itself around his paw and retreated into his cave. If he periodically looked at the ray of light instead of working, then no one needed to know.
When it happened the third time, Arthur had been waiting for it. He had been looking up into the blank absence hoping that whoever had thought of him hadn't forgotten. The thought of seeing again only to have it be taken away so abruptly pained him (the thought of never tasting that familiar light made him scream in anguish). The unparalleled feeling of relief scared him when the next piece of light descended. How was he so dependent on this mysterious stranger who did naught but send flashes of color at him? Arthur depended on no one but himself. He never needed to (You can trust me, Arthur. I'll never leave you. We have an eternity). Arthur wanted to be angry or scared but all he felt was the joy of seeing the pink and orange tendril and feeling the rightness of the bright magic emanating from it against his fins. Whatever was happening, Arthur loved it. He loved it unconditionally and painfully and never wanted it to end.
Arthur reciprocated. He had nothing as delicate as gentle moonlight or as bright as noon sunlight or as animated as sunset coils, but there was a graceful, majesty of the absolute depth of the abyss. Arthur spun his magic around the darkest, empty space and sent it upwards where he dare not go. For Arthur still had a job to do, a job he was still performing adequately even though he really had no time for distractions. This was worth the lost time. Arthur's whiskers twitched with strain and his muscles tensed under his dark, twilight scales (which he had never remembered seeing until the silver moonlight was sent) as he forced the darkness to rise and ordered the surroundings to leave it in its pure, inky black. He let it move toward the familiar, comforting taste (God, Arthur, you taste like the new moon and fresh snow. Come here, darling. I can't say away) and let it encompass the creature of light that had changed Arthur's existence so effortlessly.
The stars fell into his trench. Arthur looked up at the innumerable points of gleaming starlight and everything he once cared about (since he was doomed to this sea of despair) didn't matter because this anonymous creature of light had shown him the stars. His job didn't matter, because he'd seen the stars again and nothing mattered but meeting this creature (I won't leave you there to rot, love) and thanking him (tasting that perfect taste face to face). Arthur left his dwelling, fully spread his large fins, and took off towards the surface. He ignored the deep ache in his eyes as the light slowly built, because there was someone important waiting for him above the frothy waves (I don't care if those are your orders, Arthur. I love you) and he needed to see him now. Arthur broke the surface and suddenly he couldn't breathe, he couldn't think. Because the creature of light was there waiting for him, and he remembered.
"Eames," Arthur, the dragon of the dark, all but sobbed.
"Finally, darling, you're finished wasting our eternity at the bottom of a pit," and Eames the dragon of light stepped forward across the water to rub his muzzle against the shaking neck of Arthur. Then they were no longer in their most imposing forms. He had forgotten about this form (except for in his most confusing dreams) with his slightly large ears and dark as night hair and it felt so good to remember his skin and be wrapped up in Eames (those lips) like he had almost forgotten he wanted (needed).
"I told you I wouldn't leave you to rot in that god-forsaken pit, love." And Arthur is so glad to finally remember what made him yearn for the scent of salty air and the feeling of sunshine (and the taste of Eames, always Eames) that he didn't even mention the trouble they were going to be in for disobeying orders. They could run together in their eternity.