This post contains spoilers for the Frank Herbert-written "Dune" books.

The "Dune" book series, which extends far past where the currently planned movie trilogy expects to end, veers off into strange territory. There are major cast shake-ups, significant shifts in thematic focus, and massive time jumps. By the time you get to the fourth book, "God Emperor of Dune," nearly every character in the first book has been dead for almost 3,500 years. By the time you get to the fifth book, "Heretics of Dune," nearly every character in the fourth book has also been dead for about 1,500 years. 

Despite all those shifts and changes, author Frank Hebert still gave the series a few constants to hold onto. The first was Duncan Idaho (Jason Momoa in the movies), the only character to exist in all six books, albeit in clone form. The second and most important constant, however, was the idea of the Golden Path.