Jareth smiled the slightest bit. Sarah had been this way once, afraid of her own magic, unsure of what she could do. Of course, that hadn't ended so well, but he felt the need to allow her an out by providing his services time and again to get her out of binds. This particular one he hadn't found a solution to yet, but he was working on it.
"You must find what lets it out, Dragon," he said calmly, arching one thin brow. "That's the only key there is. Find your release point and press it without mercy. Otherwise it will stay inside and burn you from the inside out."