Found a bug where the game will end after you defeat the Zug and return to the castle (hommlet). It will show the video clip ending describing all that you did. The movie ends, shows your party in the castle, freezes and then returns to the main menu. I did go there previously and had the skull destroyed. I know that you are supposed to talk to brother smyth to normally end (7.01 NC). Bummer casue I wanted to whack rufus & burne before I retired.
That's a known bug, Gaear tracked it down in this version (his quote was "the game is actually doing what it's supposed to") and I think he will have that one fixed in the next update. I think the issue was that when you destroy the orb the game is supposed to end after so many days, and now that it doesn't end automatically with Zuggy's death, that timer can actually complete and the event fires when you re-enter Burne's castle.