The tone and sense of betrayal throughout the movie reminded me of Star Wars' The Empire Strikes Back, though this is much darker. The movie is one long escalation of loss, which happens everywhere our heroes turn. They only have small triumphs while the growing malevalence has major successes. The story progression is marked by betrayal after betrayal and evil grows in power each step along the way until by the end it appears on the verge of triumph.
The visuals are stunning and the movie is exceptionally done. However, it will be too dark for some people to deal with.