To those not of the great desert, the touch of Shai-Hulud is death
The fremen are a hardy, semi-nomadic people. They value tradition, are intensely loyal to their tribe, and are quite superstitious. Tribes may be as large as 10,000 people, and live in a cave system known as a sietch. Children are cared for and trained by the whole tribe, since the tribe’s survival depends on every member being able to carry out their duties.
The Naib is the leader of the tribe, chosen by single combat. Anyone may challenge the Naib for leadership, at any time (by invoking a Tahaddi Challenge). The Naib is advised by the tribe’s Council of Elders and Reverend Mother. Although the Naib is technically in command, he leads by consensus. If he loses the consent of the tribe, then he risks being challenged. The Fremen’s strong sense of duty to the tribe makes this system remarkably robust - challenges only really happen when a Naib fails to carry out his duties effectively.
A grown Fremen has two names. The first is given them at birth, and is the “common” name, to be used when people not of the tribe may be in earshot. The second is given when a Fremen becomes an adult, and is only to be used within the tribe.
A challenge to mortal combat, such as when challenging the naib for leadership of the tribe. The combat takes place without stillsuits, and the victor receives the loser’s water, as recompense for the water lost in the fight. The victor receives the loser’s possessions (except those that were taken during the funeral rite), and takes the loser’s wife for one year (as wife or servant), after which time she is free to choose whether to seek a new husband. While the loser’s wife is his, the victor is also responsible for any children the loser left behind.
Water is the most important substance there is. Everything else revolves around this one fact.
When a Fremen dies, their water is extracted using a death still, and added to the tribe’s store. Fremen believe that a man’s water belongs to the tribe. Their family will be given water rings equivalent to the amount of water extracted. Those who knew and liked the deceased sit in a large circle around their belongings. Each person takes an item and speaks of a time that the dead person helped them, eg: “Stilgar was my friend. When the Harkonnen attacked us and I was wounded, he carried me to safety”
If the Fremen was killed in a tahaddi challenge, the victor will receive the water rings, as recompense for the water lost during the fight.
Sayyadina means “Friend of God” in Chakobsa (the native language of the fremen). Sayyadina are Fremen women in training to become reverend mothers. A Fremen reverend mother has the same abilities as a Bene Gesserit reverend mother.
In order to become a reverend mother, a sayyadina must ingest the (extremely poisonous) bile from a drowned little maker, known as the water of life. The sayyadina must change the liquid so that it is no longer poisonous, thus becoming a reverend mother. If she fails, she dies. If she is successful, the whole tribe drink of the changed water, now a narcoleptic, leading to an orgy.
It takes a lot of training to be able to take the water of life and survive. Sayyadina are normally selected at an age of around 4-6 years old. It’s unusual to take the water of life before the age of 40. When a sayyadina takes the water of life, a new sayyadina is usually initiated, so that if the attempt is unsuccessful, not all is lost to the tribe.
The fremen believe the great worms (Shai-Hulud) are physical embodiments of the One God. They also use them as transport. Every fremen learns to ride the worms at an early age - any fremen past puberty should be able to capture and ride a worm. Tradition says that the older and larger the worm that tests a rider, the greater the things that might be expected of the one who rides it into adulthood.
There are many names for the worms. Shai-Hulud is a respectful term, and refers to their divinity. They are also sometimes known as “The Old Man of the Desert” or “The Great Maker”. It is unusual for a desert fremen to refer to a worm as anything other than Shai-Hulud, though they may occasionally refer to a worm as “Shaitan” if they are angry at the worm (Shaitan generally being used to refer to an evil entity)
Fremen are extremely capable fighters, who particularly excel at melee combat, both armed and unarmed. However, fremen fighters would be at a severe disadvantage when fighting a shielded opponent, since they are not familiar with, or trained for, the techniques required to penetrate a holtzman shield.
Ground from a sandworm's tooth, a Fremen's crysknife is sacred. A crysknife can be “fixed” or “unfixed”. An unfixed knife requires proximity to a human body's electrical field to prevent disintegration. Fixed knives are treated for storage. All are about 20 centimeters long.
Outsiders are not permitted to see a crysknife. Any that do cannot be allowed to live. Those that are permitted to see one belong to the Fremen, and may not leave Dune without the consent of the Fremen.
Fremen contact with outsiders is limited - outsiders are normally killed for their water. However, they do deal with smugglers and the Spacing Guild. They bribe the Spacing Guild with spice in order to keep the skies of Arrakis free of satellites, since such satellites would allow others to know of their work to transform the planet. They trade with smugglers, giving them spice in return for useful off-world goods.
Many desert Fremen understand standard Imperial Galach, but their native tongue is Chakobsa. The Bene Gesserit also use Chakobsa, and the Atreides battle language is a variant on Chakobsa. The native tongue for city Fremen is Galach, and some speak Chakobsa.