Futars were a genetic human/feline hybrid created by members of the Bene Tleilax who had gone out into the Scattering, allegedly as a tool for hunting down and destroying Honored Matres during a protracted and vicious war between the two groups.
However, Futars were brought into the known universe by the Honored Matres, who kept the creatures as pets. Though dangerous and harboring only sub-human intelligence they could be controlled through intimidation, sex, and emotional imprinting, typically by their owners or designated handlers.
Sheeana took 4 Futars with her during her escape from Chapterhouse. Her ship eventually folded space to the planet of the Handlers. The Handlers were first thought of as allies who hated the Honored Matres, but they turned out to be Face Dancers.
Behind the Scenes
In the book Hunters of Dune, Futars play a pivotal role in aiding the escape of Sheeana and her party from the Handlers/Face Dancers.