Differences of Ravenloft

It is a low magic setting with spell casters being rare. Folklore is how common folk understand the supernatural.
Spells that detect Ethical alignment (Law/Chaos) work as normal. However, Spells that detect Moral alignment do not work. The Dark Powers sheild evil. However, certain acts and spells are intrinsically good or evil here, and may require a powers check.
Characters who preserve their innocence are somewhat protected from the worsts horrors of the land, while those who start down the slippery slope of wickedness find it easier to find their own ruin.
Necromancy and spells that tap the Negative Energy Plane are more powerful here. Undead are also more powerful and harder to control.
Divination is less certain here. Only the Vistani can relieably reveal the future's secrets.
The Mists make travel less certain as they can appear anywhere and shift things and grab people. If a domain is closed nothing but the will of it's Dark Lord can open it again. Spells powerful could transport from one domain to another. PLanar travel is at the discretion of the mists.
The Near Ethereal can be reached. it's full of the restless dead.
Each domain has a different cultural level and is ruled overtly or subtly by it's darklord. It's darklord is both prisoner and ruler of the domain. he or she cannot leave save perhaps by death.
The Realm is ruled by the Dark Powers. It may be them which grant the cleric spells....the gods and goddesss seem distant.