Chapter Text
Merlin knows that it wasn't intentional and that Arthur was just busy with his upcoming wedding, but somewhere along the lines of "will you marry me" and "yes" a friendship was lost.
Merlin does not blame Gwen or even Arthur for that matter. Because after all, how were they to know that from the moment Arthur risked his life to find the Mortaeus flower that Merlin fell? Hard. It's not common knowledge that Merlin loves Arthur. He may stare at Arthur too long, and occasionally treat Arthur differently than other royals, but Merlin does no think that it is that obvious. And sure, it would make since knowing all that Merlin has sacrificed for Arthur and therefore Camelot. But as the only other, besides Gaius, that knows of Merlin's magic is dead, it is unlikely that anyone could know of Merlin's feelings. Actually the more Merlin thinks about it, the more unlikely it seems that anyone would know of Merlin's feelings after all that's just how Merlin is, right? But even though Merlin may act foolish and like an idiot, he is not stupid, no matter what Arthur says. He is just thankful that no one has picked up on his feelings because marrying a servant is one thing, but a male, servant who happens to be the most powerful warlock? It's inconceivable, no matter how tragic it seems. Merlin has dealt with love spells, dragons (okay mainly one), sidhes, trolls, goblins, and a world of other creatures just for Arthur. All the while, being unappreciated and ignored by everyone due to the upcoming wedding. But Merlin being Merlin has never complained about it, and is subsequently alone.
The transition back from friend to servant was subtle at first. It started with more chores than usual to hurtful insults (that even Merlin did not know if Arthur was joking or not) to overall neglect. To the citizens of Camelot it looked as if it was business as usual. The two still bickered like an old married couple and Merlin still followed Arthur to each and every event, so they did not think to question their favorite male servant. Plus, Merlin still acted as the funny, clumsy, adorable man that they all knew and loved when, in fact, he was feeling the opposite. Even the Knights, who besides Arthur (before the engagement) and Gauis, knew Merlin best, did not notice his slight shift in his behavior.
As the shift in Arthur occurred, Merlin knew he could do nothing to stop their failing friendship. Every time Merlin cracked a joke, he would be met with a grunt of acknowledgement, if that. Merlin knew Arthur was just under a lot of stress due to ruling Camelot and his engagement, but it hurt Merlin all the same.
And even through Arthur's neglect, Merlin stayed and protected the other side to his coin because he knew that Arthur would be the greatest King to ever live. Merlin believed in Arthur. He loved Arthur. And as time wore on Arthur began to act as his normal self again, and things were looking up for the two. But then Merlin let his feelings get the best of him. One drunken night spent at the tavern a month before the wedding everything was ruined: he kissed Arthur. Arthur at first reciprocated, but then he quickly realized his mistake, so he stopped the kiss and gently pushed off Merlin. Being the kind and good friend that he is (due to Merlin), he let his friend down gently, but it was never the same again.
Arthur could not stop thinking about the kiss and how that one, small kiss felt better than any of the ones he shared with Gwen. Due to his conflicting thoughts, Arthur began to avoid Merlin because after all that was the obvious thing to do, you know as opposed to talking it out like mature adults. Merlin, not being privy to Arthur's thoughts, figured that Arthur was avoiding Merlin due to the kiss.
A dark cloud began to form over Merlin's head and soon Merlin grew bitter towards Gwen for making his Arthur fall in love with her. Arthur was his to protect, his to love, and the other side to his coin, not her.But somewhere in his subconscious, Merlin knew those thoughts were illogical. He couldn't help it though. After a week Merlin realized that he was just being petty, and he felt horrible over all the twisted things he wished upon his once beloved friend. He wanted to apologize, but that would mean admitting that he kissed her fiance, and he was NOT about to do that.
So Merlin bottled all of the feelings up, and between his chores, his feelings, a despondent Arthur, and saving Camelot, Merlin, in an unlike-Merlin fashion, gave up as he could not take it anymore. So in the middle of the night, a week before the wedding, Merlin wrote four letters: to Gaius, Arthur, Gwen , and Morgana. His four most cherished friends. And with a deep breath, he grabbed his bag and made his way back to his mother. Forever leaving his friends and destiny behind.