Well, Ravenloft is a prision for the most evil dictators. But unfortunately it does not only snatch away these evildoers, but also a great deal of their countries, taking the mostly innocent population with it. Who then have to struggle in a nightmare-world.
The evil overlords have almost absolute power in their realms, but the one thing they really desire the most, they can never archieve. As a result, they are usually pissed all day and let their anger out on the population. It's a world in dire need of heroes, but even people who would be seen as heroes in other worlds, can mostly only hope to make it through a couple more days until they meet their usually sorrowful fates.