I've found Master Dunwyn is majorly bugged. This is who I assume you are referring to.
If he doesn't show up when he's supposed to teleport to Master Frederick, you can solve the problem by going to the buried statue. You will find him standing on the top of the hill there. Right click on him and he will follow you back to Master Frederick, where you can continue your conversation with Fred, who will then proceed to send you back to the hill to fight the Princess.
Also, he is quite often missing altogether from Avalon Marsh. Again, do as above, visit the buried statue, give him the letter, receive the list back from him. Go to Avalon Marsh and kill the critters. Return to him at the statue and give him the items. Because of this I make a point of visiting the hilltop before travelling to Avalon Marsh, just in case. It's a long way to go, just to get there and find out he's missing and you need to go all the way back to visit him on the hill.