Update ships were space craft that were controlled by robots, with the exception of Dream Voyager which was piloted by Vorian Atreides and Seurat. These ships held the updates that allowed Omnius to be synchronized between planets and maintain efficient rule over the Synchronized Worlds.
Most of the occurrences happened on the Dream Voyager. The first time was actually the first meeting of the two Primeros, Xavier Harkonnen and Vorian. The ship barely escaped, and the only reason it did was because of Vorian. The same ship was used to transport Serena Butler, Iblis Ginjo, Vorian, and the mutilated body of Manion the Innocent.