Poison Rossak drug was a awareness spectrum narcotic discovered by the Zensunni Wanderers during their stop on Rossak planet. "Scenes of brutal ferocity opened to her like the petals of a terrible flower. And she saw the thread of the past carried by Sayyadina after Sayyadina--first by word of mouth, hidden in the sand chanteys, then refined through their own Reverend Mothers with the discovery of the poison drug on Rossak . . . and now developed to subtle strengthen Arrakis in the discovery of the Water of Life. " ― Dune, page 235