Falling for Arthur wouldn't have been so bad, Merlin reflected sourly, if only his magic hadn't gone and developed a crush, too. It was hard enough keeping it a secret when it seemed like every other day he had to save the royal clotpole from witches, beasts, and various other ill-meaning louts. The uncontrollable, inexplicable happenings that started popping up in Arthur's presence made it very nearly impossible.
For instance:
"Merlin."
"Sire?"
"I'm sure there's a very good reason for my chambers to be covered in roses, which you're just about to tell me. Right?"
Or:
"No, Merlin, I don't believe Cook made spiced cake just because you asked. She refuses to do so except on my birthday, even when I ask, and I'm the prince! What did you do to the poor woman?"
Then, particularly notably, there was:
"If you have time to sew foppish little gold fringes all over my riding tack and make me look a fool in front of the knights, I'm obviously not giving you enough to do. Stables, laundry, firewood."
"But–"
"By midday."
Yes, Merlin's magic spurting off without his permission in a bid to impress Arthur caused him no end of headaches. Every morning he had to scramble to conceal some new token of his magic's affection, and when he went to sleep on his mattress in Gaius's chambers but woke up in Arthur's bed, snuggled intimately up to his nocturnal arousal—well, the less said about that incident, the better.
The worst part was, that wasn't even the worst part. Merlin's magic, in the most misguided cry for attention possible, started trying to fix him.
Merlin didn't especially think he needed fixing. He was clumsy and gangly and a bit odd looking and constitutionally incapable of not talking his way into trouble, and he was pretty well satisfied with himself that way. But his magic had other ideas, because before long, all Arthur had to do was mock Merlin for something or another and it would change.
"Merlin, your hair looks like someone used a mop to clean a fireplace." And Merlin's hair got short and flat.
"I could use your shirt to guide me through mountains, how do you even manage to get it so wrinkled this early in the morning?" Merlin's shirt instantly stiffened, hard as freshly boiled leather but certainly not wrinkled.
It got more personal. Merlin was too tall. Merlin looked like a lunatic when he smiled. Merlin talked too much. These were all things Arthur had said before, and Merlin was almost certain none of them were meant cruelly—that was just how Arthur was, he didn't think anything of the nonsense that fell out of his mouth. But Merlin's magic didn't seem to know that. It thought he was displeasing to Arthur and was desperate to correct it.
He could hide the changes and put himself to rights and remind himself over and over again that it was meaningless, arbitrary, not an accurate reflection of his faults; and who cared what Arthur thought his faults were, anyway. But it took a toll.
His happiness and his confidence faded a little more with each new alteration. If his magic was for Arthur, if he was for Arthur, maybe it wasn't wrong.
Maybe he was.
Maybe Arthur really couldn't stand all the little things about him that came up, and his magic was doing him a favor by addressing them. So he stopped trying to cover it up, stopped fighting it. And Arthur...
Arthur didn't even notice.
He kept calling Merlin's laugh too loud and his eyes too bright and his smile too big, no matter how quiet and dim and small they got.
It all came to a head one evening when Arthur made yet another comment about Merlin's ears. It wasn't even a criticism, not really. All he said was, "One would think that with ears like yours, you'd hear me the first time around."
Merlin felt tightening of skin as his ears, already barely recognizable as his, shrunk further in on themselves. It wasn't the first time, and it probably wouldn't have been the last if Arthur hadn't been watching Merlin as it happened.
"Merlin," he said slowly, "did your ears just..." Then he peered more closely at his servant and seemed to realize for the first time in weeks that something was terribly wrong. "You don't look quite like yourself, Merlin. What's going on?"
Merlin's laugh would've been bitter if Arthur hadn't called that insolent days ago. Instead it was soft, inoffensive, the sound barely above a breath. "Isn't this what you wanted?"
"What I—Merlin. What have you done?" It was more concerned than Merlin had ever heard Arthur, and even if he'd wanted to lie, his magic wouldn't let him.
"I don't think I meant to," Merlin said, but he couldn't be sure anymore. "It just sort of happened? It wants—you keep pointing out things that are wrong with me, and it fixes them."
"You're not making any sense," said Arthur with only a trace of his usual impatience with Merlin's prattling. "What is 'it'? A spell? Are you under some kind of enchantment?"
Merlin shook his head, unable to meet Arthur's gaze any longer. "Magic. My magic. I'm... Magic."
"You're—Merlin, if you have magic you shouldn't be anywhere near Camelot, much less in the palace where Father could find you out any moment!"
Merlin's magic rose, ready to obey no matter how much he willed it back down. Arthur must have read the panic on his face, or possibly the gold in his eyes, because he reached out and grabbed Merlin's arm before the warlock could disappear.
"I didn't mean it like that," he said quickly. "Stay. I want you to stay. And I want you to be yourself again. Your magic's just as incompetent as you are if it has other ideas. Yes, you have countless distracting qualities but it turns out I'm actually rather fond of them."