I wasn't planning on flashy magic, which means I probably could leave it a bit ambiguous. If someone was born under a good star, and especially talented at something, or folk legend said he could bring rain or heal the sick, or spook cows -- well, stuff like that happened on our Earth all the time, and was ascribed to gods, demons and magic. I would think potential readers would tend to favor a magical explanation just because of the genre, though.