Okay if the Mystics (not gonna call them fiends, bleh) can change their form to look like humans (the ones in the cathedral did, and Flea can) why didn't they just disguise themselves as Guardia guards and infiltrate the castle, kill the king, and take over? It'd have been so easy! Instead they have this roundabout plan of Yakra taking the queen and smashing the bridge (which to me still makes no sense, because then how can they get across themselves to attack the castle?). Plus, if they come out of the Magic Cave why did they leave Dorino and Porre alone? Those towns were completely defenseless yet they weren't ransacked at all.
I don't know, can someone explain the Mystic's line of thinking, because from a tactical standpoint they really blew it.