The Spacing Guild holds an absolute monopoly on interstellar travel - making it one of the three pillars of power in the Imperium alongside the Emperor and the Landsraad. Guild Navigators are humans who have been so thoroughly transformed by prolonged spice exposure that they can fold space with their minds, enabling ships to travel instantaneously between star systems without the use of computers (banned since the Butlerian Jihad). This dependence on melange makes the Guild utterly beholden to whoever controls Arrakis, and their political neutrality is maintained only so long as the spice flows. The Guild's Navigators, enclosed in tanks of spice gas and mutated beyond recognisable human form, are among the most alien and unsettling presences in Herbert's universe.