Muadru
The Brian Herbert/Kevin J. Anderson Legends of Dune prequel trilogy notes that "Muadru" is an ancient religion predating the Old Empire before the Time of the Titans. Its prophetic writings are used out of context by Iblis Ginjo during the Butlerian Jihad; there is also some indication that the Muadru and the Cogitors shared the same origin. In Paul of Dune, Paul Atreides shows Count Fenring an ancient Muadru room buried deep under his Arrakeen residence. He further explains to him that the Muadru are an ancient people who once settled through the entire galaxy but became suddenly extinct. They are believed to have settled on Arrakis while it was still a verdant planet and to have introduced the sandworms there long before the arrival of the Zensunni Wanderers.
Read more about this topic: List Of Dune Religions