As I understand it, a ‘quantum ogre’ is a piece of game content that the party will be unable to avoid encountering. It’s a way of saving on prep time for the game master but that subtly removes player agency.
For example: when the party comes to a fork in the road, will they go left or right? This provides the players with the illusion that there is a meaningful choice to be made. However, the reality is that, whichever direction the party chooses the game master will decide that the ogre is (and has effectively always been) lying in wait on that path.
How long has the term ‘quantum ogre’ been in use and from where did it originate?