What is the theme in The Waste Lands by Stephen King?

Ka-tet is the glue that holds both this novel and its group of characters together. Ka-tet is a word from Roland's world that indicates a group of people joined by fate. Roland explains that the ka-tet cannot be changed to reflect any one person's desires. Once a group is joined by ka-tet the only way this group can be broken is by death or treachery.