@Riger: To my understanding, he himself can't use powerful spells, and his way of dealing enemies using magic is to use his highly developed analysis to basically hack and take over their spells then turn it on them.
That said, I feel like we've seen what he'll do to these barbarians...
1. Grease spell that remove friction when he had that talk with best girl
2. Pram throwing that one guy off the ledge
That is to say it's time for some Dark Souls cheesing.