A sandworm is a fictional extraterrestrial creature that appears in the Dune novels written by Frank Herbert, first introduced in Dune (1965).
Sandworms are colossal, worm-like creatures that live on the desert planet Arrakis. Their larvae produce a drug called melange (known colloquially as "the spice"), the most essential and valuable commodity in the universe because it makes safe and accurate interstellar travel possible. Melange deposits are found in the sand seas of Arrakis, where the sandworms live and hunt, and harvesting the spice from the sand is a dangerous activity because sandworms are aggressive and territorial. Harvesting vehicles must be airlifted in and out of the sand sea in order to evade sandworm attacks. The struggle over the production and supply of melange is a central theme of the Dune saga. The sandworms are reverently called Shai-Hulud by the planet's indigenous Fremen, who worship them as agents of God whose actions are a form of divine intervention. The name is derived from the Arabic (šayʾ khulūd, "thing of immortality").
Conception
thumb|upright|One of the earliest illustrations of a sandworm, by [[John Schoenherr (Analog, January 1965)]]
The sandworms in Dune were inspired by the dragons of European mythology that guard some sort of treasure. In particular, Herbert referred to the dragon in Beowulf that guards a hoard of gold in a cave, and the dragon of Colchis that guards the Golden Fleece from Jason. Like these dragons, the sandworms of Arrakis will attack anyone who attempts to take the treasure that is spice from the desert sands, as if they were guarding it. In Children of Dune (1976), a character even refers to sandworms as "the dragon on the floor of the desert." However, in the story, the sandworms are merely territorial and have no use for the spice, which is in fact waste matter produced by their larvae.
In the plot of Frank Herbert's novel Dune, Herbert used the sandworms (along with the spice they produce) as a plot device to provide Paul Atreides with the trials through which he ascends to a superhuman state of being. Herbert believed that a memorable myth must have something profoundly moving that could either empower the hero or overwhelm him completely. The force in question must be dangerous and terrifying, yet somehow essential. In Dune, the sandworms serve this function. To earn the spice, humans must cope with sandworm attacks on their harvesting expeditions. To earn an even greater prize (his apotheosis into the all-seeing Kwisatz Haderach), Paul undergoes even more dangerous and transformative trials in which he risks madness and death, one of which involves the ritual sacrifice of a juvenile sandworm, and another in which he must learn to ride a sandworm.