Gwaine tended to rub people up the wrong way. He liked getting up in their faces, challenging them. This had led to many fights, particularly in his youth, and eventually, his lack of friends.
To begin with, he had rather enjoyed it. Having no friends meant no connections, no people who could tie him down to one spot, who would make him care and then throw it back in his face.
But the truth (and one which Gwaine only really admitted when he was deep in his cups) was that he was lonely. He had spent so much of his life running, he couldn't even remember when it had begun. Gwaine didn't think he knew how to stop.
For years he continued down this path, before he was halted, quite literally by the presence of Merlin.
The younger man had given him… well, a purpose, really. A friend. The one person who Gwaine thought he could really trust.
So he slowed down, stopped running from everything, stopped running from the pain, from all of his problems.
Oh, he still had problems, but now he had somebody to share them with. Finally he felt like he belonged, even when he was banished from Camelot, with no prospect of ever being able to return, he knew he would see Merlin again.
And see him again Gwaine did.
It had struck Gwaine as funny the loyalty which Merlin had towards Arthur. The idea that this scrawny man could save one of the best swordsmen in Camelot, and apparent heir to the throne was absolutely hilarious.
But then wasn't Gwaine doing basically the same thing with Merlin? Promising himself, pledging his loyalty to a man he had barely even known? There was something about Merlin, though, something which inspired loyalty, and somehow Gwaine knew that if Merlin were to ask him to follow him to the ends of the world, Gwaine would do it in a heartbeat.
There was something about the loyalty which Merlin showed to Arthur that inspired a loyalty in Gwaine towards the younger man.
And yet there was so much sadness there. How someone so… lively could hold that much sorrow behind his eyes was beyond Gwaine.
He wished he could help, saw himself in Merlin. Saw what he once was, the child, abandoned in death by their fathers, who had both left to protect their mothers. And it terrified Gwaine. Because he knew his response to leaving, had thought about it on long sleepless knights after he had become a knight, and yet he was powerless to stop it.
Could only watch as his friend spiralled further and further away, his loyalties to Arthur growing stronger everyday bordering closer to an obsession.
It was like Gwaine was leaning over a precipice, holding onto Merlin's hand, both of them tired and exhausted, but neither had the strength to pull Merlin up. So they were both just there, watching, inch by inch, finger by finger, Merlin slipped away.
Gwaine hated it. He wanted to scream and yell for the others to notice, wanted to fall on his knees in front of Arthur and beg, beg that he see what was happening to Merlin. But the only other person who would have noticed was gone, and Gwaine wanted to blame Lancelot for his friend's demise, wanted to curse the other knight for being so noble and self-sacrificing and selfless.
Sometimes Gwaine wished it could have been him.
He often wondered, late at night, what would have happened had it been him, not Lancelot, would they have mourned?
Would Merlin have spiralled as badly? And it hurt.
Hurt that if Gwaine answered this honestly, he knew that Merlin wouldn't have. He would have been mourned, yes, by everyone, but at least Merlin would still have Lancelot, at least Merlin would still have a friend he could trust with everything.
Gwaine wished he could be that friend. Wished he could help shoulder some of Merlin's burden. But he knew that he couldn't. Couldn't force his friend to tell him what was wrong. Couldn't force Merlin to tell him whatever secret he was comfortable telling Lancelot, but not Gwaine.
He could only hope that one day Merlin would feel comfortable around him to share it, that one day there would be no secrets between them, and Merlin would be able to smile again, would laugh and joke along with the rest of them.
And as he watched Merlin walk off into the cave structure, Gwaine didn't realise that he would never get the opportunity as he said goodbye to his friend for what he didn't know was the last time.
He didn't know this, not until he lay dying in Percival's arms, the poison running through his veins, wishing he could do more, anything, anything more.
Gwaine's world had gone dark for the last time, and he would never know how Merlin would mourn for him, just as he had mourned for Lancelot.