Long overlooked by the rest of the Imperium and considered backward savages, they are an extremely hardy people and exist in large numbers.

[1] In Dune, Duke Leto Atreides, his Bene Gesserit concubine Lady Jessica, and their son Paul arrive on Arrakis to take control of melange mining operations there.

Paul leads the Fremen to take back Arrakis from the Harkonnens and Padishah Emperor Shaddam IV, placing himself on the throne.

She succumbs to possession by the persona of her grandfather, Baron Vladimir Harkonnen, and Sietch Tabr leader Stilgar, his wife Harah, and Princess Irulan flee with Leto II and Ghanima to escape Alia's worsening tyranny.

Though married to Duncan Idaho, Alia takes Fremen warrior Buer Agarves as a lover, promising him leadership of Sietch Tabr in return for killing Stilgar.

In the clandestine Sietch Fondak, Gurney Halleck follows what he believes are Jessica's orders, and with the help of Fremen Namri administers an overdose of melange to Leto II as a test of his resistance to the danger of Abomination that has taken Alia.

A blind preacher emerges from the desert, guided by teenage Assan Tariq, son of Muriz from a cast out tribe of Fremen.

Desert is now limited to the area surrounding Leto II's fortress, and all sandworms other than the God Emperor have died off, thus altering the Fremen culture drastically.

The Fremen system of justice relies primarily on trial by combat, and individuals may challenge each other hand-to-hand duels to the death over matters of etiquette, law, or honor.

In the case of the Fremen, a messiah legend has been put in place that is utilized in Dune by Paul Atreides to secure the safety of himself and his mother Jessica.

Though they cross the desert on foot in a specifically nonrhythmic pattern to avoid vibrations that would attract the deadly and destructive creatures, the Fremen are also able to ride the worms by "calling" and mounting them in a ritualized, controlled manner.

Such a level of exposure to the spice tints the sclera, cornea and iris of the user to a dark shade of blue, called "blue-in-blue" or "the Eyes of Ibad".

[6] Herbert illustrates that living in the desert with no natural sources of water has spurred the Fremen to ritualize and build their society around the collection, storage, and conservative use of all moisture.

They conserve the water distilled from their dead, consider spitting a sign of respect, and put a great cultural reverence on tears.

When outside of their sietch, Fremen wear a stillsuit, a special body-enclosing suit designed to collect and recycle all the moisture the body releases through perspiration, urine, feces, and even the exhalation of water vapor in the breath.

[7] Herbert even suggests in Dune that the Fremen have adapted to the environment physiologically, with their blood able to clot almost instantly in order to prevent water loss.

The Mentat assassin Thufir Hawat is later shocked to learn that Fremen have not only overcome some of Shaddam IV's fierce and previously unstoppable Sardaukar soldiers, but have done the impossible and captured some as well.

The Fremen also forbid outsiders from possessing crysknives, and in Dune the Lady Jessica refers to "the fabled crysknife of Arrakis, the blade that had never been taken off the planet, and was known only by rumor and wild gossip."