The Dark is Rising series by Susan Cooper includes * Over Sea, Under Stone * The Dark Is Rising * Greenwitch * The Grey King * Silver on the Tree In the series, the main characters help the Light (good forces) battle the Dark (evil forces). Primarily they do this by solving various riddles or figuring out where magical objects are and overcoming obstacles to retrieve them.. These magical objects, a grail, a golden harp and a crystal sword, are hidden in different places in Cornwall and Wales. Most of the obstacles are emotional or mental: facing their fears, not giving into temptations.