The reason I chose to speak about religion through the lens of Heretics Of Dune is mainly due to the book focusing so heavily on the Bene Gesserit. This order is known specifically because of its manipulation of religion and use of it for control. The book helps narrow into the theme of religion for control and clearly this is one of the main concepts Frank wants you to get out of his series. Charismatic leaders don’t always have to be kings. Sometimes they are clergymen… 

While the Bene Gesserit use religion as a tool, other groups like the Bene Tleilax and Honored Matres use it as a shield. These groups foster a religious community in their ranks but it becomes clear to the reader that these religious beliefs are more often used as a mask for their real goals. It’s a lot easier to justify the horrible acts committed by Tleilaxu scientists through the justification of a “One True Belief”. The character Scytale seems to really believe in the religious system that his people (The Bene Tleilax) have created. He is entrenched in his own place within the religious hierarchy. He truly believes he is doing the right thing even if as the reader we may find it distasteful. 

Another interesting way to look at Religion through the book: Heretics Of Dune is by thinking about how the religion of Paul Atradies has shaped the universe at this time and how the religious rituals he established have been reshaped. By the time that Heretics Of Dune is taking place there is still religion on Arrakis, but it has been altered due to the historic events in God Emperor of Dune. Paul and his son are still worshiped on this planet, but it feels like more of a tool to control the native population rather than any sort of worship that Leto or Paul would wish for. Despite this many of the faithful on Arrakis are very much entrenched in their religious beliefs and much like Scytale their station within their religion is immensely important to them.