Enter Khrone. Khrone thought this was the Face Dancers' opportunity to take over. But Erasmus already saw the truth and depth in Duncan Idaho and knew that Duncan's powers were even just emerging. He had to laugh at what he already knew was not only a hopeless attack on the humans with their Kwisatz Haderach, but on the robot world also.
Ignoring Khrone, [Erasmus] spoke to Duncan. "I am laughing because the inherent differences between humans and Face Dancers are painfully hilarious. I hold great fondness for your species -- as more than specimens, more than pets. You have never ceased to astonish me. In defiance of my most careful predictions, you still manage to do the unexpected! Even when those actions work to the detriment of thinking machines, I can appreciate them for their uniqueness."(Sandworms of Dune, p. 475)
But Khrone was still convinced they had the upper hand and their victory was eminent. But he couldn't have been more wrong.
"Now who is drawing conclusions from insufficient data? Ever since the end of the Butlerian Jihad, when Omnius and I were sent out here on our long exile to start the machine empire all over again, I was the one in control. I allowed Omnius to continue believing he ruled everything and made all the decisions, but even in his first incarnation he was a self-aggrandizing annoyance, overconfident and unconscionably stubborn. More so that most humans!" The robot swirled his plush robes. "The evermind never learned to adapt and never bothered to face his mistakes, so I refused to let him ruin our chances again. Thus, I took control of the Face Dancer program from the moment the first of you arrived on our fringe planets."
Khrone remained defiant, though his voice carried a slightly uncertain undertone. "Yes, you manufactured us -- made us stronger than ever."
"I manufactured you, and I wisely planted a fail-safe routine in each and every Face Dancer. You are biological machines, evolved and manipulated over thousands of years, according to my own exacting specifications." Erasmus moved closer. "A tool should never confuse itself with the hand that wields it."(Sandworms of Dune, p. 476-477)
No surprise at what happens next. Death to all Face Dancers.