So the arm isn't the source of his strength. She finds that interesting. His strength may be his own, but it's clearly greater than that of an average human.

"I did not think you were using Craft," Mary says, "unless you were already an experienced practitioner." His abilities flowed too naturally. "I came here with no such prior abilities and so I am still learning how to use my jewel. So far, I'm much better at defensive actions than offensive ones."

At this point, Mary offers him her hand in greeting. "My name is Lady Mary Crawley."