Archduke was the title used by the head of some Great Houses during the time of the Faufreluches. Its owner had a high rank among the Landsraad noblemen. The title belonged to the leader of House Ecaz, sovereign of planet Ecaz. The last known noblemen who owned the title was the Archduke Armand Ecaz, who, having no heir to succeed him, retired to his estates and passed the title to the Atreides Emperor, Paul Atreides.