The "goal" of my Ravenloft campaign is to plunge the players into the unknown (I didn't tell them beforehand) and then slowly reveal a) where they are, and b) what is happening. It's a massive psychological puzzle.
While Ravenloft is a prison created by the dark powers, I also run it like a simulation, a la Westworld, Truman Show, The Matrix, and the episode "The Royale" from Star Trek: TNG.
The dark powers don't really understand mortal existence, emotions, etc. so they take a "snapshot" of time when bringing a domain into Ravenloft. That timeline then repeats over and over, and the dark lords are cursed to relive their downfall over and over again. Their torment and anguish (as well as the innocent trapped souls) is what "fuels" the dark powers.
But in order to generate new "fuel", they need a catalyst (fresh blood so to speak). Enter the players. The timeline resets when the adventures arrive and sets the events in motion again. When they break the curse or die, the timeline restarts in perpetuity. The question is whether the dark lords or the domain inhabitants know what is happening. I assume that only a very, very select few do, and some may only have suspicions.
The catch is that there are "glitches in the Matrix." As I mentioned, the dark powers are flawed and when a domain is created, they take shortcuts. If they are perceptive, the players will start to notice things are amiss. For example, the dark powers don't understand the concept of food, so the food is basically the same wherever the players go. Some NPCs may repeat themselves verbatim if the players return and talk to them again. This is especially true for the "supporting cast", like shopkeepers, commoners, etc.
There are also some NPCs that are powerful enough to maintain autonomy within Ravenloft (like Van Richten) or some memory of their previous existence that may or may not help the PCs. I also have some NPCs that were technically created by the dark powers but operate outside of their control for whatever reason, kind of like and The Frenchman and The Twins from the The Matrix Reloaded.