Arthur is dead.
Arthur is dead, but he will come back one day.
It takes two months and a horrifying dream for Merlin to properly realise the worst case scenario involved in this. He sits up in bed, swathed in sweat and shaking, tears still wet on his face. The night is still around him, that same subdued stillness Camelot seems to have these days.
In his dream, Arthur came back and Merlin wasn't there. Because it was Merlin who was dead.
What if, he thinks, it takes so long for Arthur to come back that Merlin is already dead and buried by the time he does?
There has been a tiny piece of Merlin, an absolutely minuscule piece, that remained hopeful, even in this darkest of times, because he knew, he knew, Arthur would come back one day. He knew he would see him again, even in that moment when the boat slipped from his grip, taking Arthur with it, and he sobbed in agony by that lake, wishing for that not to have been the last moment, the last touch. Merlin knew that he would see Arthur again. He knew it when he finally rode back to Camelot and broke the news to Gwen in shattered words and then hid in his room for a month. He knew he would see Arthur again.
And now this dream has broken through that hope, crushed the life out of it, and maybe Merlin was in denial for not thinking of it sooner, but his heart feels like it has broken all over again. As if the boat has slipped away from him all over again.
That can't have been the last time. Not for them, not for Arthur and Merlin. They are legends, they have done great, beautiful things. And when it came to the end, neither of them would say goodbye to the other so it can't have been the last time.
But what if it was?
No one can fight death. Merlin knows this. If he hadn't known it before, then those desperate last moments trying to bring Arthur back from death, screaming at him to come back, would have made him realise it. Death is like sleep, once it has you, it has you. And loss is a part of life. Merlin knows this, he knows all of this.
But he cannot let that be the last time.
Merlin knows what he is. He knows he is a fool in many respects. He knows that he gets attached too quickly and too deeply to people, to ideas. He knows that he is a control freak. He knows that he often cannot admit when the end is the end. He knows all of these things.
He knows, in his heart, that it is all over. But he gives it one last go anyway.
The lake laps coldly at his toes. He remembers it doing the same thing as he pushed Arthur's boat into the water. He concentrates on the words in his mind, and speaks them, and summons the Sidhe of Avalon.
They answer his call. That is the first surprise.
"You are no friend of ours, Emrys," they say. "You murdered a Sidhe elder."
Merlin thinks of that adventure with Elena the changeling and silently curses his luck.
"Do you have Arthur?" he asks.
It takes everything for him to say the words. Because they could reply in the negative, and then it really would be over and he doesn't think his heart could stand that.
Instead, after a pause, they say, "Yes."
This is almost worse to hear.
They say, "He sleeps at Avalon. He waits for when Albion's need is greatest."
And Merlin says, "I need to see him."
They say, "He will not be awake. He sleeps."
And suddenly Merlin is pushing the boat away again, pushing Arthur from him, and the pain rises inside him and he has to clap a hand over his mouth to stop himself from sobbing aloud.
"Please," he says instead. "Please."
They let him see Arthur. Arthur lies in a wide, white space, on a marble block, and he is so pale he might as well be dead, except that Merlin can see him breathing, short shallow breaths, but he is breathing.
"You cannot touch him," they say, but Merlin can watch. He watches Arthur breathing, and each rise and fall of his chest is a balm to Merlin's pain. He studies Arthur's sleeping face, engraves each feature into his memory. He could watch forever.
"When will he awaken?" he asks them.
They know. They say, "Not for thousands of years."
His worst fear is realised, and yet, in this white room, watching Arthur sleep so peacefully, he cannot bring himself to panic.
He says, instead, "All right."
The immortality potion is surprisingly easy to make, though it involves a lot of crawling around in bogs to get certain herbs. He makes it without the consultation of Gaius, or anyone else. No one even knows that Arthur is prophesied to return. Merlin has buried this little golden nugget of hope jealously inside him.
No one asks him questions, because they never do these days.
He sits on the steps of the castle one morning, while a grey dawn is just breaking on the horizon, and swallows the immortality potion whole and without hesitation.
He does not feel any difference.
He has to wait ten years before he knows that it worked.
Thousands of years later, and the boat is floating back towards Merlin, towards his outstretched hands. He touches the edge of it, up to his knees in lake water, and at last his soul is at peace again.
Arthur lies in the boat, but his eyes flutter when Merlin pulls it to the shore, and then, finally, finally, blue eyes meet blue eyes.
"I had the strangest dream," Arthur says in welcome.
Merlin is smiling and crying at the same time. He says, "Oh?"
"Yes," Arthur says distantly. "I was sleeping. For such a long time. And you were watching over me."
And Merlin says, "Always, Arthur."