core rules subtitle:
A Roleplaying Game of Galactic Intrigue based on the d20 System
from the Introduction:
DUNE: A Dream of Rain is a d20 System game based on the novels by Frank Herbert. While the game takes place on a galactic scale, most of the action is set on Arrakis, now the most important planet in the known universe. Important because it is the only known source of a spice that permits space travel, extends human lifespans and even allows humans to alter their consciousness.
from Character Classes:
Armsman, Bene Gesserit Adept, Duelist, Fremen, Knave, Mentat, Noble & Scientist