For this story to work, let's assume that Camelot is another world of its own, not medieval England.
Disclaimer: Of course I don't own Merlin or Chronicles of Narnia.
She woke up screaming and gasping for air again, although this time it was much more violent and louder than ever. Gwen rushed in as she always did when Morgana had a nightmare.
"Gwen, Gwen, this one was even worse than the others," Morgana cried.
"Shh, shh milady. It was just a dream. Only a dream," Gwen soothed. But even her maid's comfort would hardly sooth Morgana after this dream. There was no unknown threat threatening herself or her friends in this nightmare. Now, the threat was herself. She saw herself leading an army to ravage the castle of Camelot. She saw flashes of her holding a knife above Uther, reading to plunge and cause his death. She saw herself killing without a second thought, sadistically teasing those around her, reveling in death and destruction. And a strange man in red robes with long white hair and beard fighting to stop her.
"Mo," Morgana whispered. "It was more than that. It was a warning, at the very least. Or a premonition, I fear."
"I could send for Gaius to bring you something stronger to help you sleep," Gwen offered.
"I – I should go speak with Gaius," Morgana said, still clearly shaken up. She began to get up.
"Oh, no milady. I can go speak to him for you if you need a potion," Gwen said.
"No, I need to speak with him about… something else," Morgana said, shaking getting out of bed.
She barged into Gaius' chambers where Merlin was still awake.
"What is it?" Merlin asked, clearly worried about her.
"I need to talk to Gaius," she insisted.
"He'll be back in the morning. You can talk to me. You look pretty worried," Merlin said. After Morgana looked hesitant, Merlin added, "You can trust me."
"Merlin, I'm scared. I'm so confused and I need to know what's happening. Please."
"Well, Gaius can make you a remedy when he gets back," Merlin said, scratching his neck and backing away a little.
"I don't want any more remedies. They won't do any good," Morgana insisted. "I… I think I've had a vision."
Merlin said nothing, knowing that it must be a premonition, but not wanting to show his own knowledge of magic. "What?"
"I'm your friend; you know I wouldn't make this up. It was a vision. From magic," she said.
"Oh. Of course," Merlin said slowly.
"Can you believe me?" Morgana pleaded. "You think my dreams are magic too? Please, Merlin."
"I… I don't know," Merlin said, turning away from her. "What were you dreaming about?"
"Myself… I… I was evil, Merlin. Evil. I killed, I led an army, I tortured. I was practically evil incarnate," Morgana said desperately. "And… and I used magic for evil."
"Then… then it can't be real, Morgana. Because you're not evil. And you're not a witch," he said, growing less confident in what he was saying as he remembered the dragon calling Morgana a witch and saying she could not be trusted.
"But… it was so real. So real, Merlin. I need to stop this from happening. By any means possible," Morgana said, suddenly becoming resolute. She glanced around the room. There had to be several poisons here that would quickly do the trick if there was no other way.
"Just… just try to get some sleep for now. And we can talk about it with Gaius in the morning," Merlin offered. "Here, I'll mix you something for tonight."
"Thank you, Merlin," Morgana said, accepting the potion when he was finished. "Merlin, do… do you believe in fate? That are destinies are laid out for us?"
Merlin remembered the many conversations about his own destiny he had with the dragon. But to accept that fate couldn't be changed was to accept that Morgana would become an evil witch and should be stopped. "No, no I don't think so."
"Thank you, Merlin," Morgana said as she walked out the door. As soon as she was gone, Merlin went to speak with Kilgharrah.
After he explained what Morgana saw, the dragon laughed and said, "Aha! Now you see what I mean, young warlock. The witch must be stopped. Only her death will stop her dream from coming true."
"No, no," Merlin protested. "There's got to be some other way. Any other way."
"There is no other way," the dragon said.
"I can't just kill Morgana," Merlin protested.
"Then Arthur will die," Kilgharrah said.
"No! There's got to be something I can do!" Merlin insisted.
"There is nothing in this world that can stop her if the witch lives," the dragon said ominously. Merlin left the cave, visibly upset that his friend was fated to be evil. But if the dragon was right, then Merlin had to kill her. Camelot and Arthur were more important. He snuck into Morgana's bedchambers, not even sure what he was planning on doing. Morgana was pacing around the room, stressing over her dreams. Merlin wanted so much to go comfort her.
Suddenly, they both heard a roar. Morgana screamed in fear, but Gwen didn't come running this time. Surprisingly, neither did any of the guards in the hallway outside her room. Merlin stepped closer, forgetting that he was supposed to kill her and instead ready to protect her. A giant lion stepped into the room. "Greetings, Lady Morgana."
"You… you can talk?" Morgana gasped, backing away from the lion.
"Yes, I can. And I can help you, Morgana. You still have the chance to turn from your fate. Follow me to the world I created, and there you will find a new destiny for you."
"But… if I don't… then my dreams will come true?" Morgana asked quietly. It never occurred to her to question whether the lion was truthful or not.
"No one knows for sure what might have been," the lion growled.
"But… it's likely," she said. "I'll follow you. But, sir, will I ever return?"
"There are other chasms between that world and your own. You may find another and return," he said.
"How- How do I get to that world?" Morgana asked.
"Through here," the lion growled. He roared and Morgana's wardrobe began glowing. She walked to it and found herself in a beautiful field of grass, far greener than any in Camelot and full of life.
There was a searing light through Morgana's room which made Merlin shut his eyes. When he reopened them, both Morgana and the lion had disappeared. Merlin ran to the castle library to do some research. Thankfully, the librarian was asleep. Merlin almost managed to knock an entire shelf over with his clumsiness, but his magic caught it just in time. He found a book on chasms between worlds. He could hardly believe what he was reading. The different stories claimed all sorts of creatures existed in other worlds. Merlin would most definitely not have believed this book which claimed animals could talk in other worlds if he hadn't just seen one very clearly and intelligently talking just a few minutes earlier. There were very complicated-looking spells for how to open chasms and how to close them. Merlin didn't know what to do, so he did what he always did when he was uncertain how he should proceed: visit Kilgharrah.
"Back so soon, young warlock?"
"What do you know of other worlds?" Merlin shouted.
"Ahah! Why do you ask?" the dragon asked. Merlin quickly told him what happened.
"The lion must be Aslan. I was only a young dragon when I heard of him and Narnia," the dragon said.
"You know of the other world?" Merlin asked in confusion.
"Of course I do! Talking creatures of all types can live safely there. I would not have these chains holding me if I was a Narnian dragon. But I have never found a chasm there that a dragon can fit inside," he said. Merlin stared, dumbfounded. Was Kilgharrah actually sad? And even a bit jealous? That was different.
"But you have found chasms? One that I could go through?"
"Yes, young warlock. In fact, the nearest one is here in this cave. Right over there," the dragon said, signaling with a breath of fire.
"That's just a bunch of rocks," Merlin pointed out, wondering if dragons can become senile with old age.
"DON'T be so quick to ignore such things! Magic does not always reveal itself in majestic ways," the dragon boomed. "You especially should understand that."
Merlin frowned, wondering if the dragon was insulting his looks. "So the gap in the pile of rocks over there is a magical chasm to a land with talking animals. Not the strangest thing I've seen today."
"And that is the world the witch must remain in."
"Is Morgana safe there?" Merlin asked.
"If Aslan has taken her into his paws, then nothing can hurt her. But young warlock, you must make sure that she never returns to this world or she may still fulfill her dark destiny of this world," the dragon warned.
"What should I do?"
"There are magical objects that can close the chasms. Your magic will lead you to the chasms and with the right spells, you can determine which objects you need to close them. Close them from the Narnian side, or else the spell may still let her travel to here."
"So… she's never going to be able to come back?" Merlin said, a bit disappointed.
"Do you want her premonition to come true? Do you want all Camelot destroyed by her hate?" the dragon roared.
"No, of course not!"
"Then go to Narnia, and close the chasms!"