In the third Lone Wolf gamebook, The Caverns of Kalte, Lone Wolf is sent to the frozen wastes of Kalte to apprehend Vonotar the Traitor, the renegade wizard who has fled there and now rules over the Ice Barbarians.
At a certain point in the ice fortress, you will come across a stone door which, upon examination, will turn out to be a prison cell for Loi-Kymar, an elder of the Magicians' Guild. If you walk past this door without checking it, you will find yourself at section 276... from which point on the game is unwinnable.