The Once and Future King Book 1, Chapter 4
Arthur returns home, full of happiness. He and Merlyn have recaptured Cully, setting a trap without using magic, because Merlyn tells Wart, "you could not use magic in the Great Arts." Book 1, Chapter 4, pg. 32 Ector is skeptical about Merlyn's powers at first, until Merlyn creates a snowstorm in the castle! Merlyn seems to know about everything, even Kay's bullying, and at first he scolds him about it, but then gives him a hunting knife to make him feel better.