AN:

Rya3SaberVltar: First time I read its name was in a game called The Witcher (had a similiar creature) but it wasn't until I saw BBC's Sherlock, the hound of baskerville, that I learned of its true origin. The details I gave in the previous chapter are made up though.

Chapter has been modified to fill up a plot hole (as reviewed by The PhantomHokage).

A lot of dialogue but it's somewhat necessary.
Stay tuned because the next chapter will lead into Merlin's dark descent

Grey

Merlin returned to Camelot at the crack of dawn. The Barghest would not return until after dusk. Meanwhile he would have to entertain his royal pratness, the King. The manservant had forgotten almost Arthur had schedueled practice in the morning. He sighed knowing that it would be a long day. Being battered by the King was exhausting enough after a good night's sleep but Merlin didn't sleep at all and his thoughts were with the hound from hell.

Arthur seemed to notice his friend's lack of attention and he decided to quit practice earlier than usual. As Merlin helped him take off his armour Arthur began the conversation.
"You seemed a bit distracted on the field." Arthur noted.
Merlin pulled a bit of a face. "It's... Does it ever bother you?" the manservant asked.
Arthur frowned at his friend not sure what he was getting at and Merlin clarified "The people we kill and the ones that are caught in between."
"You shouldn't worry about such things, they'll only give you a headache." Arthur replied.
It's what Merlin had been trying to do for ages but the blood wouldn't wash off his hands like it did from the King's armour. Merlin's conscience had begun acting up ever since he saw Morgana being kind to the father with his daughter in the forest. There were some whom he pitied; Mary Collins, Edward Muirden, Sophia, Ulfric and even Nimueh. Others he couldn't care less about; Valiant, Kanen, Sigan, Aredian and Morgause. Finally there were those caught in between and those were the ones that burdened his conscience; Morded, Will, Freya and Balinor. One person couldn't be catagorised in any of them, namely Morgana. The pain she had caused fell on his shoulders because he helped create the darkness that now surrounded her. He felt responsible not only for the pain she brought onto other but the anger she kept holding on to as well.

"When Morgana 'caught' me we ran into a man and his daughter. They were looking for the druids-"
"They've been dealt with." Arthur said in a dismissive tone that shocked Merlin.
The manservant had expected a different response altogether. Arthur was acting as if he had said he saw a bandit escaping rather than a confused man with his daughter.
"Killed?" Merlin's question made him sigh.
"They're not always as innocent as they look." Arthur didn't even make an effort to hide his annoyance and displeasure towards his manservant's sympathy.
One would expect that, after Mordred, the King would have grown a bit more leniant towards the druids. Although they lived in his Kindom, Arthur did not see them as his subjects because they didn't act as such. A true King would either hunt them as rebels or embrace them for the lost souls they were. In his ignorance he dismissed them. For a King, ignorance was not bliss but damnation.
"What about the Knights that died in the ambush?" Merlin asked.
"They were good men. They didn't deserve to die at the hands of bandits." He replied.
It seemed a decent answer but the words sounded hollow and with the illusion of honour in death. Good men, yes, that he was right about that but the bandits part was rubbish. Those men didn't deserve to die at all. It was the end of life and leaving everyone behind with a pain that might never heal. All these nearly political answers made Merlin want to hear something real.
"People died for you, do you even care?" The manservant lashed out and Arthur gave an immediate response.
"They knew the risks! I can't mourn every soul that dies in the name of Camelot." The King spoke like his predecessors.
Not only he speak with the typical arrogance of a King but the mentality of his words were those Merlin would attribute to war. What was it doing in this time of peace?
"But you don't even care!" Merlin raised his voice and hoped Arthur would see reason, "The men that died for you were fathers, brothers and sons."
"I don't want anyone to die, but as long as Morgana is still out there I don't have a choice." Arthur explained.
Their struggle against Morgana was the war Arthur was fighting. In his mind at the very least. It was a fair reason but considering 'choice' he was wrong.
"There's always a choice." Merlin said softly.
Arthur shook his head and smiled bitterly. "Lifting the ban isn't a choice. She'll raise an army of sorcerers and burn the city to ashes."
"She wouldn't." Merlin said without thought.
"How would you know? No matter how much you want it, she's not the Morgana of old."
He looked away out of shame. Not shame for his hopes but the hopes he destroyed, her hopes. It infuriated him that Arthur believed his manservant didn't fully comprehend the severity of things. He had no idea of the sacrifices made for him and no bloody right to say it either. It was him that first knew about Morgana's betrayel, not the King.
Merlin took a deep breath and took a gamble by taking out the dagger she gave him.
"What's this?" Arthur asked bewildert.
The manservant wet his lips. If this went wrong then it would be the end of him.
"I bargained with her for something to banishing the hellhound with." He confessed.
Arthur looked at him wide-eyed as if he had grown another head.
"And she gave you this in exchange for..." He trailed off.
"A rare ingredient." Merlin wanted to keep him in the dark for his own good.
"For what purpose?" Arthur spoke as if interrogating him and it wounded him.
Arthur was the authority of the Kingdom, one to be respected, but this wasn't the way friends behaved around each other. Merlin thought the events in the forest proved he wasn't enchanted and could be trusted. Apparently the King still had his doubts.
"Growing." Merlin replied, "I know what she plans to do with it. At least trust me this once."
Too late did the warlock realize his rather poor choice of words. "How can I trust you when you deal with Morgana behind my back?!"

The man had a fair point but the alternative, telling Arthur where Morgana lived, would've been far worse. The witch wouldn't allow herself to be captured and he wouldn't hesitate to kill if need be. The worst case scenario would be both their deaths and the curse of the hellhound would have remained for many more months.
"Morgana wants the throne but there's no point in it if the city is empty. You can't afford to view the world in black and white anymore, Arthur."
The blonde took another deep breath. Merlin was pulling his words of wisdom card again. He hated it when he did that, especially because he was right. Arthur didn't even bother to ask how he found her. All they knew was that she was somewhere in the Valley of the Fallen Kings. Those were her hunting grounds. So to speak with her had to be done on her terms or she would not show. The King could guess Merlin went there alone and waited for her to find him.
"It's the necessary evil." Said Arthur as he turned the blade and examined the other side of it.

Merlin shook his head in denial. He didn't understand. Good and Evil belonged to black and white. The only necessary evil Merlin knew was the moment he poisoned Morgana. In shades of grey it was the closest thing to black.
"It's the grey area where we saved the druid boy and Ealdor. You do what you think is right." Merlin said but in the back of his mind the sentence continued "And damn the consequences."
The thought almost made him flinch. He quoted her without meaning to. If she had remained in Camelot with a hopeful heart then Arthur would have been a much more sensible person by now. Morgana knew how to push Arthur buttons, always had, like brother and sister.
"Like Lancelot's knighthood." Arthur seemed to understand the concept.
The warlock was glad Arthur's rage had left him unscathed. "I don't even have to muck out the stables." He thought with a hidden smile.
"All that's left is killing the hellhound."

They waited until dusk before starting their patrols. Each squadron of had a banner carrier and several men on the walls of the citadel kept an eye on them. If any of them went down, that's where the barghest would be. Merlin wanted to vanquish the hound on his own but Arthur, who then held the magical dagger, didn't let him. The King had taken upon himself the task of slaying the beats with the short, pointy weapon. Magic made him uncomfortable. Not even the fact that he controlled the enchanted blade eased his mind. He kept shifting in his saddle, something not gone unnoticed by Merlin.

The warlock told himself it wasn't magic but the shortness of the blade that made the King feel uneasy. Slowly but surely he began to understand how and what Gaius was towards Uther. Gaius kept secrets and in return Uther turned a blind eye. It wasn't friendship. It was mutual captivity behind a mask of civility. He also saw how he and Arthur were becoming the very same thing only their captivity was destiny. He wanted friendship, not some loathsome game of civility.

Merlin was almost glad when a banner fell in the lower town as it took his mind off his troubles and back to the matter at hand. Arthur left the citadel with a small number of Knights and raced through the gate. The hellhound acted as if he had been caught in the act when the Knights arrived. It did not flee this time, its hunger for blood was not yet sated. It leaped and knocked one of the Knights off his horse. Immediately it dug its teeth in his shoulder and the man's screams were unbearable.

Before Arthur had time to respond it jumped at him as well. Fear saved him as he toppled back before the creature reached him. As unlikely as it may have been, paws broke through part of his armour. The King was off his horse but the hound had not managed to launch himself on top of him as he had done with the other Knight. The other Knights shouted in chaos as their leader quickly grabbed the dagger. Not knowing of the magical dagger, the Knights surrounded the King as a way of protection. It did not matter to the cursed beast as he tore another Knight off his horse and landed straight in the middle of their protective circle. Arthur was confronted by foul, red eyes. It roared once and his arm flew forwards, digging the blade into the dark being of magic. It jumped up and scattered into a billion pieces carried away by the wind like sand running through fingers.

No one saw the gold fade from Merlin's eyes. Arthur was petrified at the close-up of the beast's eyes as it had nearly paralyzed him the first time he saw them. This would become some heroic story in the history books where the mighty King defeated the hound from hell. They wouldn't mention the equally heroic manservant that got the dagger from his murderous half-sister. As long as magic would return to Albion, Merlin couldn't care less. The Fomorroh found find its way back to Morgana in the childish manner of knocking on her door and running for the hills. It was cowardly but Merlin didn't want to face her if he didn't have to. It would only bring pain to the both of them.