A land is reigned by a circle of powerful men who control every aspect of the citizen's life. This cabal changes members often. In reality, the spectres of a small necromantic covent possess and control the people in power. Since they simply possess the bodies, they can leave when old age overcomes their shells and possess a new up-and-coming noble.
A village where everyone goes blind sometime during puberty. What could be causing this? Perhaps something in their diet. Or some malignant gene. How would an entire village where only young childen can see function?