Wallach IX was a Synchronized World during the ancient times of the Butlerian Jihad. When Yorek Thurr abandoned the League of Nobles, he was appointed its ruler, by the Thinking Machine ruler, Omnius.
When the planet was to be obliterated during the Great Purge, Thurr abandoned the planet and retreated to Corrin. The Titans then settled the deserted planet, while Porce Bludd with Quentin Butler scouted it for survivors. It was there that Quentin Butler was apprehended by cymeks.
Over the next millennia, it served as the main planet for the Bene Gesserit Sisterhood. By the time of the late Corrino Empire, the Mother School was located there, as were extensive training facilities. Almost all sisters underwent training at this planet when situation allowed.
During this time, the planet was surrounded by a defensive shield which was impenetrable, as was shown in 10,175 AG, when a Guild heighliner crashed into the barrier. Most of the highliner broke up in the Wallach atmosphere, with some major pieces striking uninhabited areas of the planetary surface.
A few decades later, after the Ascension of House Atreides, during the Regency of Paul Atreides sister, Alia, the still active Bene Gesserit Council on Wallach IX filed formal protest against House Corrino, in the matter of the assassination of young Leto Atreides II.
Thousands of years later, a Mentat Duncan Idaho ghola visited Wallach IX during the time of God Emperor Leto Atreides II's reign, to suppress a Mentat school the Sisterhood had thought they had hidden there.