Tau

Tau is a mystical concept of the Fremen, expressing the oneness of a sietch, the sense of community and their devotion to it. The tau of the sietch was at the heart of the balance between spiritual beliefs and the rules of survival.

It must be noted however that the tau concerned the oneness of each specific sietch; there was no tau among the entire Fremen peoples.

Those who did not follow the tau and the principles of the sietch were expelled from it into the desert. Therefore betraying the sietch was equal to psychological and physical suicide.

Tau Orgies brought the sietch into a physical and spiritual intimacy with visions showing the "ways of their fathers" and an ultimate bond with past, present and future, obtainable only through participation of the entire sietch.