Game-wise, Fremen function as Feral Worlders with several differences.
Fremen do not have the Iron Stomach trait, due to their largely vegetarian and Spice diet, instead replaced with a starting weapon, the Fremen Kris Knife
[Knife - Melee, Thrown - 3m - 1d5+1 R - Pen 0 - Primitive - 0.5 kg - cost 10 - Unique to Arrakis]
Fremen PC have only a 50% chance of having the Rite of Passage trait. The lifestyle of the Fremen is rife with infighting due to the greatly honour-based society, and the commonality of duels in said society. The treatment of wounds after the victory of such duels is the greatest way a Fremen learns to treat wounds. The other 50% of Fremen PCs, because of the Fremen's near-heretical ties to their rendition of the God-Emperor, following a variant of the teachings and lifestyle of the Cult of the Holy God Emperor, under their Bene-Jesuit beliefs, which give them a link to the Warp, may take a single Psychic Power from the Divination or Biomancy Psychic Disciplines.
Fremen may automatically manifest this power at its Threshold, automatically rolling on the Psychic Phenomena chart.
Fremen, because of their regular contact with offworlders, do not suffer from the Primitive penalty Trait. Instead, they suffer from the Water-Wise penalty Trait, from their upbringing.
Water-Wise: PCs with this penalty Trait incur Fellowship penalties when interacting with individuals or groups that unnecessarily use water. These penalties are at the discretion of the GM. In extreme instances, the GM may solicit an Ordinary [+10] to Hard [-20] Willpower test. On a failure, the Fremen PC must make an unarmed attack against the offending individual or a member of the group, with no possibility of killing the target. On two degrees of failure, the Fremen PC will draw a weapon and attempt to punish the offending individual or a member of the offending group with a single attack, with the possibility of killing the target.
In the case of extreme failure [three or more degrees] will engage in combat with the offending individual or group member[s], with Surprise being used to the Fremen PC at the GM's discretion.