The average person from the majority of realms in Ravenloft knows:
The name of their “realm” and neighboring “realms”, and the most important rulers of those lands.
Magic is an unfamiliar, dangerous thing that is best left to those magic-using types, who should be avoided.
Many dangerous creatures lurk outside their village; they will know some of the details of the most common animal nearby, and some details about a species of monster if it commonly preys upon humans. Paridon has rumors and superstitions, but rarely anyone sees a true monster.
Of the many dangerous creatures out in the world, there are a few that look like men. Some are called dwarves, elves, gnomes or halflings, though the differences between them aren’t really clear. Some folk trade with these queer folk, but its safer to avoid them.
The land has always been the way it is now. Any talk about Grand Conjunctions or demi-planes is just a lot of nonsense – mostly from those magic-using types.
No one knows what’s beyond the Mists, and no one wants to know.
From time to time, strange people might appear with strange clothes and languages, who might claim to be from some land far away. Its best to keep your distance from these people; they’re often magic-using types, and always trouble.
The Vistani are a strange type of nomads who wander all over the land. Sometimes they put on shows outside of town. Some are thieves and conmen, and others can tell the future, but all at least seem to have eerie powers.
Common knowledge varies from domain to domain; certain peoples have more experience with phenomena such as magic and divine clerics, while others do not. The following is a short list of exceptions to general knowledge:
The Vistani know a great deal about the demi-plane, including information about domains, darklords, magic, curses and many species of monsters. They will not, however, speak with the same terminology familiar to players.
The people of Darkon have more experience and comfort with demi-human races.
The people of Hazlan have more experience with arcane magic due to the number of wizards retained by their lord Hazlik.Merchants and sailors may know a great deal about traveling through the Mists, as well as the mistways that link domains.
The people of Lamordia do not believe in the supernatural, nor do they believe in gods of any kind. They are aware of many scientific phenomena.
Some domains have an active clergy, and can produce priests with sufficient training and faith to use divine magic. In these domains, commoners may be more familiar with divine magic and healing.