The High King takes place in the mythical world of Prydain. Although there are many strange creatures that live in this kingdom, this mythical land seems parallel to our world in many ways. In an "Author's Note" Alexander comments: "While it grew from Welsh legend, it has broadened into my attempt to make a land of fantasy relevant to a world of reality."

The time of the story is irrelevant because it is fantasy, but it is important to note that there are no motorized vehicles. All transportation is by foot or on horseback. Communications are either by human or animal messengers.