The Secret Keeper
The first thing Gwaine noticed about Merlin was that he was gorgeous.
The second thing was that he was a bit of a lightweight when it came to mean, which a very big mouth.
The third thing he noticed was that he had plates flying without touching them.
But, well, it was a fight and many chaotic things were happening, he thought that maybe he had imagined it, because the smile Merlin gave him when he introduced himself was so big, so honest, that he didn't seem to be keeping any secrets (and keep a secret he must have if he was using magic so near Camelot).
On the following days, he discovered a number of things about his new friend, all of which pointed to him not being the kind of guy that would dabble with magic (Gwaine never thought all sorcerer's were evil like it was said around this parts, he knew it could be used to good things as well, but it didn't sound like Merlin). He completely forgot all about it until they met again, on their way to save Arthur from his own ridiculous quest. He wasn't particularly close, but he had heard the dwarf saying something about magic and ran to them – he wasn't going to let Merlin be turned into a toad or something – but his following words were what actually confirmed Gwaine's first suspicions.
"Strength has arrived".
Of course, it could only be a figure of speech. Strong as Gwaine might be, he wasn't some sort of personification of the idea, he didn't think so, anyway. He rather run away then face commitments, and strength was about so many things beyond being a good fighter. And Merlin didn't have to be a sorcerer to be Magic, for his charisma was a spell as powerful as any enchantment. Maybe this is what the dwarf was talking about.
One way or the other, if Merlin was indeed magical, it was up to him to tell Gwaine about it when he felt ready. He could wait.
And wait he did – while he watched Merlin doing impossible things and pretending they were coincidences. He waited while him and Lancelot somehow made an army of immortals turn to dust (Lancelot must know, there had always been something of a secret between them. Once he had thought it was how Lancelot felt about Gwen, but there was no way that a single person in the whole of Camelot didn't know about it – Lance was as competent in hiding things as Merlin was). He waited in the long year that followed, and if it hurt that Merlin didn't trust him, he pretended it was nothing.
He even considered confronting Merlin about it when he survived the dorocha, it had been clearly said that no mortal could survive them, but as they mourned Lancelot's sacrifice, he allowed it to slip away. Many times during the following months he tried to make Merlin see that he would be there for him whatever happened, but Gwaine had never been good with showing how he felt. He insisted on going with Arthur to look for Merlin even after everyone had lost hope. When Gaius was named a traitor and disappeared into the night, he ignored Leon's orders to check upon Merlin – he could play soldiers when there weren't more pressing concerns. He didn't leave him any choice but to have company while looking for Gaius, and didn't even bother to offer him the torch when they parted – surely Merlin could get himself his own light.
Merlin didn't notice any of these things.
And maybe, had things been different, he would have let the matter go once again, but then Lamia showed up.
Gwaine couldn't remember much about the moments he had been under her influence, but he could see in Merlin's nervous eyes and badly hidden flinches that it must have hurt more than physically. He knew then he had waited far too long, and all the friendship they had built would vanish into nothingness if he didn't make a move now.
It wasn't easy to find Merlin alone, Arthur had him running around all day, but in the end, it all worked out simply as he stumbled on Merlin polishing Arthur's armor in an empty room.
"I'm sorry."
Merlin looked up quickly, startled by his presence, like a deer in the sight of a crossbow, and while he wanted to ease him, he knew better than to try and reach for him.
"What for?"
"What happened with the Lamia."
The younger man shrugged.
"You were enchanted."
"I would have liked to think that I'm a man that wouldn't harm you even under an enchantment" said Gwaine, deeply. "But I am not that man."
"You are not to blame" said Merlin, firmly.
"You tried to warn us" he said, softly. "You weren't enchanted."
Merlin tried to hum nonchalantly, but he failed miserably to do so.
"Merlin"
He waited until his friend looked at him to say the following words.
"I know."
"What?" said the servant, at first, scared; and then, remembering himself. "I have no idea what you are talking about. Have you been drinking again, Gwaine?"
He chuckled, and Merlin grinned, clearly more comfortable with his presence now.
"I'm serious, Merlin. I know, and I have always known – suspected, at least – since we first met."
Merlin's mouth hanged open, clearly trying to formulate some random excuse.
"I won't tell – your secret is safe with me."
He still half expected a lie, something that he'd have to fight, risking losing it all or gaining everything, but Merlin seemed to think better of it.
"Thank you."
"Don't thank me" said Gwaine, a sad smile upon his face. "You are my best friend after all."
He turned and left before Merlin could answer – this had been enough, more would be too much. And as he walked away, he wondered if he would ever be able to tell Merlin his own secrets as well.