What is the theme in The Dark Tower VII: The Dark Tower by Stephen King?

Fate is the main theme here. In The Dark Tower VII: The Dark Tower, fate, or ka, is the wheel that makes the world go around. Roland Deschain and his ka-tet, Susannah Dean, Eddie Dean, Jake Chambers, and Oy, have all been brought together by fate, brought together on an important quest. Fate helps them as they make their way to the Dark Tower, and other people are drawn to them by fate to help them succeed in their quest. Fate is what allows them to succeed and empowers them. Unfortunately, that empowerment is lost when Eddie Dean is shot and killed.