Fair warning: when you return to town with the Diadem, the characters in the party will retire, and you won't be able to use them any longer, although they will remain in the roster for you to view. (Characters that are not in the party when you bring the Diadem back will remain accessible, as they were.) Consequently, don't return with the Diadem until you're done with your characters. If you want to defeat Murkon but want to continue to explore, you can drop the Diadem (and try recovering it again later). If you want to save any gold or items for other characters, then leave that stuff behind with another character before you set out to win the game.