I did just let one of my heroes advance from the Barbar role to the Paladin role and had to notice that I cannot switch back to the former role apparently. Is this impossible at all or is there a way to changed roles back? This was one of my favorite features of Wizardy! Why shouldnt it work with W&W?

If and when you decide to reset all the game quests - wipe the board clean so to speak - you will be able to change a character back. Within one game, though, you cannot. I found that a disappointment.

Wyv