Oh, so he wasn't a demon. Is this lightning spirit related at all to Lucina's shadow? He certainly shouldn't be related to Lucina not being able to use magic. In fact he should have nothing to do with Lucina at all. That being said, since spirits are related to magic, maybe he actually could help Shizuru to figure out Lucina's problem. If one of the fundamental spirits can't see what's wrong, nobody can.