Status Updates From La grotta di cristallo

The climax seems to be coming down to a sword fight, which is pretty unsatisfying. Since the beginning we've been told in no uncertain terms that Merlin isn't a warrior. It seems like a pretty big miscalculation for him to keep ending up in fights with bigger, stronger men, and it doesn't really measure anything he's been cultivating. What happened to the fire blast he learned in that cave??