Deep within the bowels of the castle, where the stones whispered of ancient magic and long-forgotten secrets, Merlin sought the counsel of the Great Dragon, Kilgharrah. The air was thick with the scent of earth and the echo of dripping water, a symphony of the subterranean world.

"Kilgharrah," Merlin called into the darkness, his voice steady despite the uncertainty that gnawed at his heart.

The dragon's eyes opened, glowing like molten gold in the shadowy cavern. "Young warlock," Kilgharrah's voice rumbled, "what brings you to seek my wisdom at this hour?"

"Morgana," Merlin began, his brow furrowed with worry. "She has joined forces with Morgause, and together they threaten Camelot. I need to know how to protect the kingdom."

Kilgharrah's gaze was ancient and knowing, a starry sky captured in his eyes. "Morgana's destiny as a dark witch has been woven in the stars for eons," he intoned. "It is a path she must walk, as it is written."

Merlin's heart sank, a cold dread settling in his chest. "Why was I not made aware of this?" he asked, a hint of accusation in his voice. "Why have you kept this from me?"

The Great Dragon shifted, the sound of his scales like the clinking of chains. "There are truths that even I must tread carefully around, Merlin," Kilgharrah said, his tone solemn. "Destiny is a tapestry of countless threads, each one vital to the whole. To reveal too much could unravel the very fabric of what must be."

Merlin absorbed the dragon's words, the weight of his responsibility pressing down upon him. "What must I do?" he asked, his voice barely more than a whisper.

"You must trust in your own power, in the role you play in the unfolding of these events," Kilgharrah advised. "Protect Arthur, guide him. He is the once and future king, and in him lies the hope of Albion."

Merlin stood before Kilgharrah, the weight of Camelot's plight heavy upon his shoulders. "Kilgharrah," he said, his voice echoing in the cavernous depths, "do you know of the Obsidian Order?"

The dragon's eyes narrowed, and a low growl reverberated through the chamber. "Yes, young warlock," Kilgharrah replied, his tone grave. "The Obsidian Order was a cabal of sorcerers whose power once threatened the very fabric of the world. Their ambition knew no bounds, and their dark arts were feared by all."

Merlin's hands clenched into fists at his sides. "And if they were to come back to power? If they were to join forces with Morgana and Morgause?"

Kilgharrah's growl deepened, and the air around them seemed to grow colder. "If the Obsidian Order were to rise again and ally with the sisters, their combined power would be nigh unstoppable," he warned. "Such a union would spell doom for Camelot and all who stand against them."

Merlin's mind raced with the implications of Kilgharrah's words. The threat was greater than he had imagined, and the need for action more urgent.

"Then we must ensure that does not happen," Merlin said, determination steeling his voice. "Thank you, Kilgharrah. I will do whatever it takes to protect Camelot and its future."

Kilgharrah's gaze held Merlin's, ancient and inscrutable. "Merlin," he intoned, "you must study the Tome of Ashkanar. While it was created by one of the founders of the Obsidian Order, the magic within its pages is potent and profound."

Merlin's eyes widened. "But that book… it's filled with dark magic," he protested.

"Indeed," Kilgharrah agreed, "which is why it must not fall into the wrong hands. The knowledge contained within could be catastrophic if wielded by those with ill intent. However, for one who walks the path of light, the insights it offers could prove invaluable."

Merlin nodded, understanding the gravity of the dragon's counsel. "I will study it, then," he said, "and ensure its secrets are used for good, to protect Camelot."

Kilgharrah's eyes seemed to soften, just for a moment. "Be cautious, young warlock," he warned. "The line between light and dark is thin, and even the purest of intentions can be corrupted."

With a final nod of respect to the Great Dragon, Merlin left the cavern, his mind already turning over the possibilities of what he might learn from the Tome of Ashkanar, and how it might aid him in the trials to come.

Merlin ascended the stone steps to the quarters he shared with Gaius, his mind a whirlwind of thoughts and fears. The air was thick with the scent of herbs and potions, a comforting familiarity amidst the chaos.

Gaius looked up from his work, his eyes reflecting concern. "Merlin, what did the dragon say?" he asked, setting aside his mortar and pestle.

Merlin took a deep breath, steadying himself. "Kilgharrah spoke of the Obsidian Order," he began, "and the danger if Morgana and Morgause were to learn of it. He believes their combined power with the Order's knowledge could be devastating."

Gaius nodded gravely, the lines on his face deepening. "The Obsidian Order was a dark chapter in the history of magic," he said. "Their return would be catastrophic."

"They must not find out about it," Merlin said, a determined edge to his voice. "And I must study the Tome of Ashkanar. There may be something within its pages that can help us."

Gaius regarded Merlin with a mixture of pride and worry. "Be careful, Merlin," he cautioned. "That book is filled with dark magic. It is not to be trifled with."

"I know," Merlin replied. "But it's a risk we must take. For Camelot."

Together, they turned their attention to the ancient tome, its pages filled with secrets that could either save or doom them all. The fate of Camelot hung in the balance, and time was running out.