It was common belief in medieval times that goods and property could only be affected by the Fair Folk, the faeries, if it was acquired unlawfully or unfairly.
The gold hoops and rings that sailors wear are to throw into the sea if there is a storm. These are bribes to the sea gods to let them live through the storm.
Once a year, the king steps down from his throne, and lives as a peasant for one day, the next day is the anniversary of his coronation, and it is celebrated by a reenactment of the ceremony. This is doubly beneficial, firstly, because the people are able to have the grand parade that always precedes the ceremony. Secondly, because the heir to the throne is given a day on the job every year. Although, apparently, the thought has not yet come to one of the kingdoms enemies, the assassination of the king during the renewal coronation would be a moral, as well as a political blow to the kingdom.
One morning, the sun does not rise. It seems that a great darkness has settled across the kingdom - at first, it is merely an inconvenience, but as time passes and plants begin to sicken and die, some action must be taken. As the deluded King plans the sacrifice of fifty tender virgins in the name of the Sun God, rumours spread of an ancient barrow uncovered in the hills...