A/N: Hello, all! So, this is just an oneshot that has been bouncing around in my brain for a couple days. Kind of just an introspective piece about Merlin's magic with the idea that he can feel when Arthur is around. I don't own Merlin, the BBC does. Any reviews or favorites would be greatly appreciated. Enjoy!

Arthur's very presence made Merlin's magic jump to life. A tingling in his fingers and a dizzying rush of clarity. He could feel the power surging through his muscles, just under his skin, begging, persuading, forcing him to let it out. It made his heart pound and his stomach flip. He loved it. It was a thrilling sensation, knowing that he had the power to bring the very sky and earth crashing together or the great stone walls of Camelot tumbling to the ground with just a look, a thought, a whispered word. When he was around Arthur, it was not hard to believe his destiny. It whispered into his thoughts with each pump of his heart Emrys, Emrys, Emrys, you are the mighty Emrys. The greatest warlock of all time. Around the King of Camelot, Merlin could look in a mirror and see the two greatest figures in history—the King and his sorcerer, Arthur Pendragon and Merlin who the Druids called Emrys, two sides of the same coin, destined to unite all of Albion. He could see them standing, Courage and Magic, side by side, so powerful and so great that armies would turn and run at the mere mention of their names. He could feel his eyes start to burn gold and his thoughts would switch, without him even knowing, to the language of the Old Religion, the language of Magic, his true natural tongue. It was exhilarating and terrifying and absolutely addicting.

The first time he felt his magic surge to the surface with the force and overwhelming suddenness of a great river bursting through a dam, he thought it had been anger. He had not had a problem keeping his magic in check for several years, and it had never been so intensely, obviously there. But as soon as he saw that boy, the one who was throwing the knives at that poor servant, Merlin's magic leapt to his fingertips. It was that that had made him act so foolishly. The rush of power so strong it made him lightheaded and, apparently, stupid. But the magic settled back into its usual place, thrumming through his veins with his blood, gentle and warm, as soon as the guards removed him from the side of the blonde prince.

The second time was remarkably similar. It had never been so easy to call on his magic as when Arthur had been swinging his mace and laughing at him. His senses were all overactive, picking up on every smell, sound, or color around him. His entire being was consumed with the most intense warmth he'd ever known. And when the prince called off the guards and said Merlin's name—there's something about you, Merlin. I can't quite put my finger on it—a tingle went up his spine and made his ears buzz.

What he couldn't figure out was the third time. Arthur was there, true, and his smirking was annoying. But Merlin wasn't angry, he was enjoying himself, talking with Gwen and observing the nobles. And yet, his magic was swirling and coursing through his veins, his muscles, his very being. And when he saw the knife, saw the witch throw it at Arthur, every ounce of magic he possessed surged forward, slowing time itself down, and his whole being cried out "save him."

As each meeting with the prince came and went and they were each filled with progressively less anger and much more laughter, Merlin came to the only conclusion that made sense. It wasn't anger that had triggered his instinctual magic, it was Arthur. Just Arthur. Every time Merlin was anywhere near him, whether it was on a quest or just passing each other in the hall, his magic would jump to the surface, race through his mind. As the prince and his manservant, his warlock, his friend, grew closer, Merlin's magic was a source of energy and power, an almost constant high that Merlin would miss every night when he was excused from service. It would always be there, pounding and rushing and surging, fighting to be used, always less than a thought away. It would come without being called when Arthur was in danger, screaming at Merlin in its strange, ancient tongue protect him, save him, protect, protect, protect.

Merlin had grown to expect the reaction when the prince, now king, was around. Even after all these years of being with Arthur every day, its intensity had never dulled, never become ordinary or boring. It made Merlin feel strong and important and very, very unique. If Merlin's friendship with Arthur alone wasn't enough to make him stay by his king's side—which, without a doubt, it was—the way his magic felt when their eyes met or they spoke would have kept him there anyway. The thing that had changed throughout the years was the fear that one day, one minute, just one second, Merlin would lose control. That he would forget his undetectable battle and his magic would break free, soar out of his fingertips, turn his eyes blazing, burning gold. And Arthur would know. He had not been afraid at first; the worst that could happen was that Uther would have him killed. Now, however, he was terrified in ways he had never known. If he lost control, Arthur would know. And preventing his king from thinking that Merlin had betrayed him was more than enough reason to fight his instinct, struggle against the power that wanted to get out so badly.

Arthur's presence made Merlin fight against his nature. His presence made Merlin feel power so incredible he almost couldn't control it. It changed Merlin, the king's optimistic, talkative manservant into Emrys, the warlock of legends, myths, and songs. It made his entire being thrum and pulse. It could slow time, magnify sounds, and make colors so intense and complicated it took Merlin's breath away. It was the most wonderful, most encouraging, most intense feeling Merlin had ever experienced. And yet Merlin—wise, powerful Emrys—had no way of knowing that his presence made Arthur feel almost exactly the same way.