Merlin spent the walk to the kitchens and then to Arthur's chambers thinking. He didn't want to kill Morgana, but he couldn't contain her magic forever, and he didn't know anything that could get rid of her magic permanently. There was a chance that Kilgarrah knew, but the dragon had also told Merlin multiple times to kill Morgana.
"You're silent today," came Arthur's voice, breaking Merlin out of his thoughts. He looked at Arthur to see him staring back, an expression of curiousity on his face. "What's the problem?"
"I don't know what to do about Morgana," replied Merlin. "The easiest solution would no doubt be to just have her executed, but I don't want to have to kill another magic-user."
"What else could you do?" asked Arthur.
"There might be a way to permanently bind her magic," replied Merlin. "It would make her a much smaller threat, but I have no clue if it can actually be done."
"Would Gaius know?"
"Probably not," said Merlin, "but Kilgarrah might."
When Merlin got to the meadow, Kilgarrah was already there. "Greetings, young warlock," he said. "Is anything the matter?"
"Do you know of anything that could permanently bind another's magic?" Merlin asked.
"Why do you want to know?" replied Kilgarrah.
"Because I can't bind Morgana's magic permanently," replied Merlin. "And I'd rather not kill her."
"You have the Witch?"
"Yes," said Merlin. "So do you know of any way to permanently neutralize her magic?"
Kilgarrah was silent for a few seconds, before he said, "There is a creature called the Gean Canah, which can drain the magic from a person permanently. However, it is hard to summon and control."
"If it can drain Morgana's magic, I'll control it," said Merlin determinedly. "Thank you, Kilgarrah."
"It is no problem, Merlin," replied Kilgarrah. With that, he launched himself into the air, disappearing from sight in seconds.