Arthur wasn't entirely sure how old he was at this point. He'd known in his first life and probably could have calculated it out after the first few, but by now he had no idea.
He'd drawn out a few rough estimates though and the results were. Well. Frankly unbelievable.
It wasn't surprising that he'd started to forget things was what he was saying. It was kind of surprising that he was still . . . functional, but he'd noticed his memory had odd quirks it didn't use to. He suspected that something (Destiny, he remembered, every time he died) was keeping back memories he didn't need so as not to overwhelm him. (Later, he suspected that she also kept back others for the sake of her own amusement. Arthur was less amused, especially considering what had happened to his father the first time around.)
He forgot things, or he forgot the right context for them, but sometimes he could pass it off as normal.
He forgot his wedding anniversary. That was what Jennifer thought at least because it fit with her idea of who he'd been in Camelot before being reborn into England.
The truth was that he'd remembered his anniversary. The wrong anniversary, the one he shared with Gwenhwyfar. He'd thought he still had four months to go, but he'd gotten it wrong. He blushed and apologized and bought her the most expensive flowers in the shop and let the others tease him. He told himself this was normal, this was fine, lots of guys did this, and he was fine.
He wasn't the only one who forgot things. Those times when Merlin had been left to wait alone, he tended to forget a few details as the years passed. He asked Arthur to remind him sometimes - little things like what exactly he'd said at the Yule festival, sometimes, and big things like what his mentor's name had been others. It was the action that he forgot mainly, confusing details of this battle or that, allowing painful memories to be replaced with something gentler or something he'd seen or heard about elsewhere.
Merlin would turn to him with desperate eyes and ask question after question, trying to sort what was real from what was not, when Arthur wasn't always sure himself. He corrected Merlin's version of Camlann without thinking, and then, watching him panic and struggling to help, beat himself up, because how could he know? Maybe he was the one who was confused.
He forgot, sometimes, when he woke up which previous life this incarnation was tied to. If his friends were there, he could sort it out, but if it was just him alone, at least at the moment, he could never be sure. They didn't rotate in order.
He'd regained his memories once at the same time as Morgana, and he'd waited for her to make the first move because he couldn't quite remember whether this should be heartwarming, awkward, or life threatening. Morgana's reaction hadn't clarified matters which was unfortunate because he could hardly just go ask her or Merlin, "Beg pardon, I can't quite remember. Did Morgana kill my wife, or was Morgana a trusted adviser? Her hair was red both times, and I can't quite recall."
Actually, he couldn't have asked that even if they wouldn't have looked at him like he was insane because he didn't talk like that. The point still stood though, and forgetting whether someone was friend or foe wasn't normal.
(Well . . . There was that one time. But that wasn't so much forgetting as rapidly changing alliances, so that was different.)
He started leaving himself lists. This is your wife's name. This is how you died. This is your anniversary. This is the name of your son. This is where you work. This joke will make sense. This joke will make a knight punch you.
They're very helpful lists, right up until Gawain finds one and hands it to Genevieve.
For the first time, Arthur wonders if maybe he was wrong to think it was only Merlin's soul that was fundamentally the same. He sees something in their eyes he hadn't expected to, and despite the seriousness of having to talk his way out of concerned suggestions of therapy, it makes him feels better somehow for the thought.
He loves Guinevere every time. Always Guinevere, no matter how different. Had he always glimpsed the same bright soul?
He shakes the thought off and returned to defending himself. He ends up going to see some sort of memory specialist. Arthur pretends it helps and starts hiding his lists.
He can't stop writing them. In his next life, the world's too far gone to have anything resembling specialist doctors and everyone's gone a bit mad, so he wears it more openly, jotting down notes onto his hand, letting the words scrawl up his arm when he runs out of room. Merlin, perhaps thinking the notes are a form of note tags, adds "If found, please return to Emrys," while he sleeps. He laughs until he realizes the words won't wash off and have a magical signature that will instruct the reader how to do exactly that, and the consequences if they do not.
"You've changed," his friends start telling him, and they sound questioning, because to them he has been dead for a thousand years or more, so how could he change?
How can he tell them he has spent ten thousand years fighting since he last saw them?
But Arthur is still Arthur, and he can't remember most of it, so he lets himself fall into whatever feels natural and it works most of the time.
He forgets that Merlin has lived through - not as much, perhaps, oddly, but enough. Enough to see it in his eyes and demand answers when he isn't too badly hurt by events.
Sometimes Arthur steals tricks from his old friend and puts him off.
Sometimes he tells him.
Merlin believes him. It's odd. Countless variations and yet Merlin always believes.
His reaction varies. He always tries to help, of course, he's Merlin, but whether it's with jokes or tea or advice changes. And one time, there's one time, where Merlin looks at him and asks what he remembers of their previous life, and the conclusion is, as Merlin sums up, "Less than I do, but enough," and he seems so oddly cheerful that Arthur has a terrible, dreadful suspicion that he's happy to be remembered at all, and that makes Arthur a little bit sick because Merlin is as devoted as ever. Arthur will see Merlin again and again until it all blurs together, but Merlin in this reality remembers everything about Arthur more sharply than he does himself.
He brands that memory into his head and tries to remember everything after that, but it falls through his arms like a child trying to hold too many cookies at once.
He forgets that Destiny is jealous. He forgets that she will steal all memory of Merlin in that reality just to spite him, just to give it back and watch him burn with guilt for letting it go. He forgets that every moment of happiness they eke out they must pay for.
He forgets that Destiny will kill them. He forgets that Destiny will torture Merlin again and again, whenever he turns away from the path she has laid for him.
Merlin will forget it too. Merlin, who is the same, but always, always forgets, just like the others. But while Arthur might forget the details or the cause, he will remember other things.
He remembers Gwaine dying because of his stupid mistake. He remembers Guinevere dying, alone and betrayed, because he had put his people before her. He remembers Merlin giving him a cheerful salute before sacrificing himself to save Arthur's son.
He remembers getting Gwen's name wrong and the hurt in her eyes. He remembers making a joke that hurts Percival more than he'd ever let on. He remembers punching Morgana when she'd done nothing wrong.
He remembers being too late to fix any of it.
So next time, even though they don't remember, he gets his anniversary engraved on his ring and makes a list of all of Gwen's favorite things and gives her a picnic in the middle of a war. He picks her up and whirls her around and makes careful note of everything she tells him and does whatever it takes to get that wonderstruck look of love in her eyes.
I'm sorry, he whispers right before he wakes her from a nightmare. He hunts down rabbits so she can have the fresh meat she's been craving for breakfast, and he smiles when she asks why.
He takes an arrow for Gwaine and ignores everyone who shouts at him afterwards. He makes sure the knight knows he is valued and tosses him an apple and doesn't answer when Gwaine asks how he knows that he likes them - it wasn't something he would have had a chance to notice, the first time.
Arthur remembers something he read once about universal constants and laughs.
He defends Percival from society's jeers in a world where he's been judged by "The Test" and found wanting and memorizes what Percival will laugh at and what makes him flinch and makes sure never to do the latter.
He rises from the lake and Merlin runs to hug him and won't let go for a long, long time. Even when he does, Merlin walks too close to him so that their shoulders are constantly bumping, and it takes Arthur to realize that Merlin's panicking when they're briefly separated by a crowd. Only when they touch is Merlin sure this is real, so he throws an arm around Merlin's shoulders and pretends not to notice his half ashamed relief. He never mentions it when Merlin peeks into his room in the middle of the night.
One of them, all of them eventually, makes a mistake.
Sorry. Sorry, I'm so sorry, it won't happen again. I'm sorry.
He forgives all offenses against himself instantly, every time.
He cannot remember his father's original face. He can, however, remember if not all, than enough of what they have done for him and what they have suffered.
He remembers what he owes them and he makes lists of the rest.
Remember you must die, a poster says.
Arthur stares at it for a moment then adds a modified version to his list. He has no trouble remembering his impending death, but it does take some effort to remember that someday it will stick.
Remember. Remember your lists, remember their lives, remember, remember, remember.
So naturally, next time, Destiny takes it all and laughs.