I'm skipping The Death Song of Uther Pendragon, because I wasn't sure on how to incorporate Ella into it, so I'm going into Another's Sorrow now. If you have any suggestions, please let me know :) Anyway, enjoy!

"I would not test me if I were you," Morgana warned Mithian, "You would not enjoy the consequences."
"Where are you going?" Mithian asked as Morgana headed for the door.
"To visit the young and former princess of Metin. I have some business to discuss with her."

Ella laid on her bed, watching the flame of the candle. A knock sounded on the door. Ella came up to it and opened it to what she assumed was princess Mithian's servant - Hilda. "Can I help you?" She asked curiously as she waited for the spill word. Something to do with her eyes was scarily familiar... "Don't you recognise me?" Morgana teased in her old woman's voice, "Your powers are strong and you are clever. You must realise by now."
"Get out of Camelot, you witch," Ella said, her voice dangerously soft as she stepped closer to Morgana. She wasn't strong enough to fully destroy Morgana, but she could try.
"You and I are the same, Ella."
"I would never be so twisted as you are. You tread a dangerous path that will only lead to your own destruction."
"And I will gladly bring down Arthur if my path is destructive. Now goodbye, Ella. You will not breathe a word of this to anyone until it is too late." Before Ella had the chance to defend herself, Morgana used her magic to tighten her throat. Ella suffocated until she collapsed onto the floor. Morgana took out a vial containing a deep red coloured liquid and poured a few drops into Ella's mouth, then disappeared out of her chambers.

...

"Good morning, Lady Ella," Merlin greeted casually as he came into her chambers in the early morning, "Sorry to wake...you..." He trailed off as he saw her lying on the floor, her red hair sprawled all over, and he came to her, checking if she still lived. He sighed in relief as he saw her breathing, and lifted her up and onto her bed before running out to get help.

He returned with Gaius, the king and queen and a few knights. "What happened?" Arthur asked as Gaius looked over Ella. "I don't know," Merlin replied anxiously, "I came to her chambers to say good morning and I found her unconscious on the floor."
"We must still help Mithian."
"What about Ella?"
"I will look after her," Gwen assured, "I have done it before and I'm sure some of the knights will help too. Gaius, can we help her?"
"It is a very simple cure and can be easily prepared but it will take a few days until she will awaken again. I shall quickly get it for you, my lady."
The physician headed out.
"Thank you, Gaius."
"We should prepare to depart Camelot," Arthur stated, and kissed Gwen, "Goodbye, Gwen."
"Goodbye, Arthur," Gwen said sadly as her husband and most of the knights walked out.
Merlin kissed Ella's forehead then followed Arthur, who suddenly stopped and looked back to see Mordred sitting on Ella's bed next to the sleeping girl. "Mordred," he called, "Come on."
"I would rather stay here, my lord," Mordred replied, "I can be more useful here than if I go with you. I have some knowledge of medicine that may be useful."
"Your choice, Mordred." The king sighed, and continued on his way so they could prepare to depart Camelot.
"You should go with the king," Gwen noted.
"As I said, my lady, I would be more use here."
Gwen frowned in wonder, "Why do you care for her?"
"We were childhood friends," Mordred explained, "She probably doesn't remember me now, but we used to play with each other. The Druid woman that her parents had employed to teach her sometimes took her to my village after we fled Camelot. We became good friends."
"You should tell her when she awakens. She needs someone just like I need Arthur."
"It's not quite like that, my lady. She was a princess, I was just a boy."
"And Arthur was once a prince and I was once a mere serving girl. Everyone has someone."
Mordred smiled at Gwen, thinking of what could once have been his future. Morgana had changed that, but he was glad he had been reunited with Ella all the same.