Tleilax is the sole planet of the star Thalim, noted as "renegade training center for Mentats," specifically "twisted" Mentats. The homeworld of the Bene Tleilax, its capital is named Bandalong and most of the planet is off-limits to outsiders, as the majority of it is considered holy by the religious Tleilaxu.
Read more about this topic: List Of Dune Planets