“What if they’re hypersensitive to magical fields? What if they can get hurt by them?” Old mare’s tales told of such mythical creatures—but what if such creatures actually existed? He had trouble imagining how to cure anypony without resorting to magic. “What if . . . maybe where they come from, there aren’t leylines. Maybe just occasional spots of magic. This . . . thing could warn them before they set hoof into such a place.” Eager to prove his theory, he levitated over a spare heart monitor and dialed the sensitivity all the way up.