A/N: I thought that Merlin letting Morgana give him this Fomorrah was a ridiculous premise, as Merlin would never let even possible hurt come to Arthur for any reason, given that it's reasonable for Merlin to think it might expose his magic, too.
This took hold of me while re-watching the episode. It may continue, it may not. But here it is for your enjoyment anyways. Starts off during the episode 'A Servant of Two Masters.'
"Fomorroh are creatures of dark magic."
Merlin didn't like the sound of that. Dark magic, so dark even Morgana called it dark magic. This was decidedly one of the worst situations Merlin had ever found himself.
"Even if you cut off their heads, you cannot kill them. Another will just grow in its place."
He looked at Morgana with trepidation as she walked closer. "In the days of the old religion they were revered by the High Priestesses, as they allowed them to control people's minds."
A sense of violation struck Merlin, not unlike when he found he'd been undressed and redressed while unconcious.
"Fomorroh will suck the life force out of you. Everything that makes you Merlin will be gone. And in its place will be one thought."
Morgana's intentions were clear - manipulate Merlin, get him to kill Arthur. To Morgana, Merlin was an underestimated servant close to the king, one who would be capable of dispatching of Arthur with mundane means.
Morgana was a dangerous enemy, but very predictable. All she did was hatch plans of varying complexity to kill Arthur, and this seemed to be one of her simpler ones. More immediately dangerous was the Fomorroh.
"One thought that will grow until it's consumed you completely. One thought that will be your life's work. You will not be able to rest until it's done."
He could take his chances with the Fomorroh and hope Gaius could stop him, or break out right now and reveal himself to Morgana. But he knew better; Gaius could not stop him or his magic, and Arthur was so defenseless against the cleverness and magic Merlin had been hiding for so long. If the Fomorroh took control of his magic, there is no way anybody would be able to stop him, and Merlin would never forgive himself. Well, that decides that.
Morgana knowing he was a sorcerer would be problematic, but he'd take Morgana exposing his secret to Arthur over a dead Arthur.
"And that one thought is simple. You must kill Arthur Pendragon."
Merlin went limp as he shouted "Onbindan! (untie)" He fell to the floor as Morgana gasped, wrenching his hand free of the ties. He scrambled around on the floor, shouting "Ådlþracu gegrind! (force of impact)"
The shelf next to Morgana fell on top of her, giving Merlin time to escape the hut. He scrambled to his feet and shakily launched himself through the hut door. He got about 50 feet outside of Morgana's hut before he heard her behind him.
"Ástríce!" She shouted, throwing him across the forest. The impact shook Merlin badly, but he didn't have time to nurse his injuries. If Morgana caught him, he'd be in a much worse situation than he was before. Merlin stumbled up as he ran, dodging Morgana's spells.
"Fylwérig! (stun)" The witch cried. He saw a bolt of light pass next to him as he slowed time to leap behind a tree. It missed him by inches.
Merlin took off running again, turning as he ran to yell "Fréosan! (freeze)" He combined the spell with his command of time to freeze Morgana in place, but the spell missed and she kept running behind him.
He saw Morgana's dress and had sudden inspiration. "Becnyttan! (tie/bind)" He cried, tangling Morgana's dress beneath her feet and tripping her up. Merlin didn't risk looking back to check up on her.
Merlin willed time to slow and ran faster from her, not letting his exhaustion getting the better of him. He was out of her grips in a couple of seconds, her movement slowed behind him.
Merlin looked around, guessing he was in the white mountains, deep within the forests of Camelot. He knew Camelot was only 2 or 3 hours ride away from here, making it easy for Agravaine to find her.
He ran for as long as he could, but passed out near the thick trees outside Camelot. Captivity and magical exhaustion getting the better of him, he slowed down and immediately unconciousness overcame him.
He was woken not long later by none other than Gwaine. "Merlin!" He shouted joyously. "It's good to see you mate." Merlin saw the other knights of the round table behind him. "What happened?"
"It's Morgana," Merlin said, clambering to his feet. "I found her hideout - she took me captive, I escaped."
"You escaped? On your own?" They asked with disbelief.
"We need to get back to Arthur, capture her before she gets too far. She'll be fleeing now that I know where she is, and we have to strike now."
Gwaine's face grew serious, as did the two other knights who were with him. "Lets go," He said, as he pulled Merlin onto his horse. They rode hard and were back in Camelot within the hour.
Merlin characteristically burst into the council room. "Sire!" he said, aware of the councilmen in the room.
"Merlin!" Arthur exclaimed, frustration at the interruption forgotten. "It's good to see you!" Merlin waved him off before he started in on the joyful reunion routine.
"It was Morgana who captured me," Merlin said. "She took me to her hovel. I escaped, but if we don't act fast she'll abandon it. If we hope to capture her, we need to leave now."
Arthur's face hardened, and he turned to the council meeting. This was the opportunity they'd been waiting for. "I'm afraid this meeting is adjourned," Arthur said shortly. They nodded in understanding. He turned to the knights of the round table that were present. "We ride immediately, go let the others know. How far is the journey?"
"Not two hours if we ride hard," Merlin said in response.
It was less than two hours later that a large group of knights arrived at Morgana's hovel. "We're here," Merlin said. "It's just inside these doors." Arthur led the group inside and pushed it open, Merlin entering behind him.
The hovel was abandoned. The potions which littered the shelves were gone, and only tattered furs remained of Morgana's clothing and blankets. It looked as if it had always been abandoned.
"We're too late!" Merlin exclaimed. He pounded a wall in frustration. "I'm sorry, everyone."
"Well, it's at least worth taking a look around for clues," Leon said.
"Maybe we can track the bitch," Gwaine agreed.
"Elbogan ond clústor! (shut and lock)" Morgana's voice cried out suddenly. The door swung shut and locked behind them. As soon as the shock registered on their faces, they heard Morgana say "Befón eac beadumægen. (contain with force)" Runes drawn around the edges of the hut lit up, and a red shimmering wall covered the inside of the hut. Morgana then emerged from a cupboard in the hovel.
"What have you done!" Arthur exclaimed. Gwaine beat against the door behind him, but the force of the impact never reached the wood. Even Percival's blows did nothing, his broad fists beating uselessly against the force-shield.
Out of the corner of his eye, Merlin saw Elyan try and rub out the drawn runes on the floor, but knew erasing them would do no good. More likely than not, Morgana bound this spell to herself instead of leaving them in flimsy runes. How she had set up a complex spell so quickly, he had no idea.
"You know very well what I've done and what I will do," Morgana said. "Thank you Merlin, this was better than I'd ever hoped for." Merlin scowled in return and Morgana smiled sinisterly. Dread settled into Merlin's heart at the darkness in her eyes.
"Oh, not only for bringing him to me," Morgana crowed, "But for the chance to break his heart, like you broke mine."
Morgana was going to reveal Merlin's secret to Arthur just to spite him. Just for revenge. Morgana knew Merlin would never betray Arthur, but Arthur saw the very possession of magic to be betrayal in himself - he would be left with nothing.
Merlin considered that this would happen, that Morgana would reveal him, but not so soon. Not in the same day.
Merlin's face twisted in anger at Morgana, and hurt crossed his features as he turned to Arthur. "I'm so sorry, Arthur." His tone was grave, dire.
Arthur put his hand up, dismissing Merlin handily as he always did. "You did not intend this," he said shortly. "I know you are no traitor."
"Oh, don't be so sure," Morgana crowed. "Merlin has a secret you don't know." Arthur's eyebrows merely raised, so sure was Arthur of the notion that there was nothing Merlin would do to earn his anger.
Merlin looked at Morgana with more betrayal than he'd ever felt in his life. Morgana was crushing his life into pieces right before his very eyes for the fun. This was no longer about the freedom of magic, or oppressed people - this was cruelty for it's own sake.
"Oh don't look at me like that," she spat. "After all, you hid from me too."
Merlin's face twisted in pain. "And it breaks my heart that I had to, Morgana. I blame myself for what you've become, or at least - I blame myself for not trying to talk you out of it."
He then turned to Arthur, eyes watering and seriousness in his gaze.
"I want you to know that whatever happens, whatever has happened and whatever will, you know me. You've always known me." His tone was deep, and it got the attention of his King - this was not Merlin apologizing for leading them into a trap. Arthur's eyes grew serious as he knew something bad was happening.
Behind him, Morgana sadistically enjoyed his pain, a smirk growing on her face. Her blue eyes glinted wildly, but Merlin forged on.
"I was always and still am the clumsy idiot that brought you your breakfast, and I am still happy to be your servant until the day I die. I would gladly die for you. None of it was a lie." Merlin had a tear tracking down his face.
Dread pooled in Arthur's heart, and adrenaline was beginning to pound through his veins. Morgana was here and they were in her grasp, and yet she stood here cackling about a 'secret,' and Merlin stood before him begging Arthur to remember what he already knew.
Although Arthur often wondered why Merlin was prone to bouts of depression and melancholy, he thought that he might be about to find out.
Gwaine spoke up before Arthur could. "I'll make sure he knows." He gave Merlin a meaningful look, and Merlin momentarily entertained the idea that maybe Gwaine knew his secret already.
Arthur opened his mouth and motioned to speak, but Morgana silenced him.
"Béon forswigian, (be silent)" she incanted dismissively, and the next words out of Arthur's mouth came out with no sound.
"I will tell you what is going on, dear brother." The spat the last few words. "Your precious Merlin is a sorcerer."
Arthur looked at Merlin with abject disbelief written all over his face, and the charm on his voice was gone.
"No," he said, shaking his head. "He can't be," he said with disbelief, disregard. "Have you seen him?"
"Luckily, we have a way to prove it," Morgana crooned. "I've invented a spell, you see - if a person has magic, it forces that magic to the surface." An evil leer broke out on her face. "I hear the more magic you have, the more painful it is." She turned her head to Merlin, and fixed her eye on him.
So she wouldn't just let him show Arthur herself, she was going to force him to show just how powerful he was. From what little Merlin understood, he was very powerful, and that force was going to be paraded around, and would destroy his own life.
Merlin, at least, wouldn't be mistaken for being on Morgana's side now - If he was Emrys, the all-powerful warlock, he knew he wouldn't survive such an ordeal. He readied his magic to fight back inside of him, but stilled to let this conversation finish.
Arthur held up a hand. "I thought people had to study magic to learn it, and that every sorcerer made that choice." Arthur narrowed his eyes in the direction of his sister.
Morgana laughed. "This is the legacy of Uther," she spat. "Magic is a gift. You are born with it, and if you do not learn to control it it will eat you away from the inside. If you have magic and do not learn sorcerery, you harm others, or die yourself."
"That is not true," Arthur said. "People make the choice for magic themselves." Arthur's tongue curled around the word 'magic'.
"If that was so, why did Uther execute children?" Morgana sneered.
Arthur fell silent as Morgana laughed. "But I digress. Let us see if your servant has magic. Oh, and Merlin?" Morgana smiled wickedly. "This will hurt."
Merlin quickly brought his arms up to lash out, and Morgana revealed a blade floating at Arthur's throat in an instant. "I wouldn't fight this, if I were you," she threatened, already prepared for Merlin's reaction.
"Åcumendlicnes mægen sé drýcræftas cwylla wiðer gewill! (bring with force the magical well against the will)"
Merlin felt his magical core ripping up against himself. Normally such a pure and whole feeling, his magic was now tearing against him as it burst forth.
He felt his eyes burn and felt the power of his magic swirl around him, hot on his skin. He felt it go out into the hovel, filling up the room, and he felt himself draw from the earth as quickly as the magic left him, the power of the very earth flowing through him. He had never brought his magic to the surface before with such force, had never even tapped a tenth of the power.
It would be a beautiful experience if it weren't against his will, dragging his body out, being ripped out of him despite his desperate attempt to control the fury that would tear his friends and Morgana apart.
Merlin pitched to his knees, and then fell to his hands and closed his eyes against the rushing noise in his head. He was dimly aware of his magic swirling around him in a thick golden mist. He felt screams tear from his throat as he saw his golden magic swirl around him, and as he screamed they lashed out like whips at the cabinets, cracking them in two.
He could feel the walls cracking, and clamped down harder yet to control the force, only multiplying his agony as his magic was drug out of him with yet more agony.
Dimly, he heard Morgana's wicked voice in the background. He bit his screams down to listen, panting hard against the rushing wind in his ears. Merlin couldn't breathe.
"The evidence is before your own eyes," Morgana said. "And I must say, I'm surprised at the amount of magic he has. I've never seen anyone with this much before."
"You're doing this to him, somehow. I won't let you set my best friend up!" Arthur cried, fighting the evidence of his own eyes.
"No," Merlin panted. He looked up and his golden eyes met Arthur's, which turned away in revulsion. "I only use it to protect Camelot," Merlin cried. He screwed up his face in pain, closing his eyes against his friend's betrayal. "I only use my magic to protect yo-" Merlin's speech cut into a scream, as Morgana threw out her hand and cried spellwork.
"Ådl!" pain "Why do you defend Arthur so! He would have you killed, all of Camelot would have you dead!"
Merlin's felt his heart crumble into pieces, into dust in the wind. What was the pain of being opened to all of the magic of the earth forcefully, next to the pain of a best friend believing you're lower than human? Arthur now saw him as nothing more than a monster of magic, born to die.
All of Merlin's hopes that Arthur might accept him were dashed, torn apart by a vindictive witch which poisoned everything she touched. Merlin even saw that he had been foolish to ever hope that - he did everything he could at every turn to show Arthur magic could be used for good, but for the King of Camelot it was always perverted and ruined. It was not unreasonable for Arthur to see magic as evil, when it had taken everything from him.
As if to prove her wrong, Leon drew his sword and said "Stop what you are doing, Morgana! It's purpose has been served - stop hurting Merlin."
Morgana pouted. "But it's turning out to be so much fun, watching my brother squirm. Tell me Arthur, what will you do about this sorcerer?" She tauned. "Will you have him sent to the pyre too?" She cried against the wind.
Merlin grit his teeth against the force and cried out, "If Arthur sends me to the pyre, I'll light it myself, Morgana! I will never betray him." His screams continued.
All the knights eyebrows raised into their hairlines, except Gwaine. "Remember Arthur," said Gwaine warningly. "Remember what he said."
The knights around him looked at Arthur, clearly pleading him to stop what was being inflicted on Merlin.
Arthur's stomach turned at the implication. It seemed evident all of them, even Elyan, still trusted Merlin - at the very least, they didn't want his pain to continue, even though he was a sorcerer. Magic took everything from him, his family, friends, Gunivere's family, most of Camelot had lost at the hands of this evil, and yet his supposedly honorable Knights of the Round Table wanted him to spare the most powerful sorcerer they had yet come across, who was a liar and betrayed the kingdom to boot?
But when he turned to the sorcerer on the floor, what thundered through his veins was not anger at an enemy of the state, but empathy for his best friend who even now was fighting the evil of Morgana, even when he knew it would probably get him executed. Arthur had his secret, private doubts about the laws of magic, but he had not dwelled on them in years, not since the death of his father at the hands of a vindictive old man. But Gaius had always said it was not the old man's fault, and that he made an honest mistake. And even now, Merlin the Sorcerer refused to bend knee to Morgana, the most powerful and maniacal witch seen in decades. Would not an evil such as magic immediately join with her once revealed?
But Merlin lied to him for so long - it could be a front, it could all be a front by an impossibly clever liar. Merlin was either no liar at all, or the best one he had ever seen.
Arthur's indecision was evident on his face - it was tearing his heart apart to see his best friend being put through this but at the same time, every fibre of upbringing told him he shouldn't care now that he knew he was a sorcerer.
Either he had to accept not all magic was evil, now, and save his best friend, or he had to leave him to Morgana and end the matter.
Merlin raised his head again, tears streaming from his eyes and his cries of pain forming words meeting Arthur's gaze.
"Please, Arthur…" Merlin begged. "If you're going to kill me, do it now."
That was all it took for Arthur to finally become the deserving King of Camelot. This was no evil, kneeling before Morgana and bent by her torture - only a good man would still be fighting, as Merlin clearly was now.
His heart told him Merlin had done nothing wrong and that he didn't deserve this pain, and if Gwen and Camelot (And Merlin) had taught him anything, it's that his heart wouldn't lead him astray.
"Stop doing this to him, Morgana. Nobody deserves pain such as this." Arthur's voice spoke with a kingly commanding tone, while fear lanced through the leader's body. It was true; he would not torture even the worst sorcerer just to spite him, a deplorable behavior.
Morgana cried as she broke the spell and Merlin crumpled to the floor.
"Why would you spare him and not me!" she cried. "He is just as much a sorcerer as I am!"
Arthur began defending his decision in spite of himself. "Merlin has not murdered in cold blood like you, Morgana. Merlin has never thrown any rightful ruler off of their throne, God knows why if he's a sorcerer. Merlin has never betrayed secrets of Camelot like you have." Arthur found himself believing his own words the more he went on, his speech losing his cold authority. "If Merlin has magic, he has certainly never used it for evil like you."
Morgana flung her arm out, but Merlin reached out his just in time and cried "Åsælan híe forhíe! (bind movement for them)" She stopped moving and seemed unable to move or speak, as though bound tight with ropes. But her eyes were flashing gold, and magic was welling around her quickly.
Merlin quickly but shakily sat up, and cried quickly "Líesing fram befónir beadumægen! (release from containment of force)" The shield in the hovel disappeared, and the runes darkened.
"Run," Merlin said shakily. Gwaine went to help him up, but Merlin brushed him off. "Morgana's going to break out of my spell any second-"
Just then, Morgana stumbled with a flash of her eyes, free, and cried "Forþ fleoge!"
The knights flew back but Merlin cried "Åþwænan! (soften)" before they hit the wall. When they hit the wall, the stumbled and were thankfully still conscious and able to fight.
Merlin wasted no time in flinging both of his arms out and yelling "Bealucræft bordrand! (magic shield)" A magical shield was erected in between Morgana and them, her spells hitting the shield and dissipating upon impact with the shimmering energy.
However, Merlin was quickly weakening from the effort of the spell, sinking into the floor from his exertion.
"Go back to Camelot!" He said with urgency to the knights. "I can deal with Morgana for now. Go, tell them she got away!"
"What of you?" Gwaine asked hurriedly.
"I'll be fine," Merlin said, waving his hand. "Now go!" They saw the shield fracture for a second, and needed no more encouragement to file out the door.
Arthur was the last to leave, and even in his old age he never forgot the look Merlin gave him as he passed through the door. His eyes looked back, and despite the gold in his irises his eyes shined with a loyal sincerity, and his mouth turned upwards into his old, encouraging smile.