Extreme temperatures and treacherous weather events make life outside the cities of Arrakis truly hostile, with sandstorms powerful enough to cut through metal. Only the native tribes known as the Fremen have adapted well enough to survive. Preferring to inhabit the remotest regions of Arrakis, the Fremen share the deep desert with the giant sandworms known to the Fremen as Shai-Hulud. Long exposure to spice has given the tribe their characteristic blue eyes, the Eyes of Ibad.

Little else is known of the Fremen, except that they are dangerous and unreliable. Fremen attacks make spice harvesting extremely hazardous. For the Fremen, spice is the sacred hallucinogen which preserves life and brings enormous health benefits. For the Imperium, spice is used by the navigators of the Spacing Guild to find safe paths between the stars. Without spice, interstellar travel is impossible, making it by far the most valuable substance in the universe.