The sandworm is a fictional form of desert-dwelling creature from the Dune universe created by Frank Herbert. They first appear in the 1965 novel Dune, considered to be among the classics in the science fiction genre, and are iconic of the Dune series.
In the series, the sandworms — called Shai-Hulud among the Fremen of the desert planet Arrakis (Dune) — are worshiped as manifestations of "the earth deity of Fremen hearth superstitions." The Fremen believe that the actions of the sandworms are the direct actions of God, and so the worms have been given numerous titles such as the "Great Maker" and the "Worm who is God." Virtually indestructible and with indefinite lifespans of potentially thousands of years, the giant sandworms are also referred to as the "Old Man of the Desert", "Old Father Eternity" and "Grandfather of the Desert".
Sandworms are animals similar in appearance to colossal terrestrial annelids and in other ways to the Sea lamprey. They are cylindrical creatures with no significant appendages, equipped with a fearsome array of crystalline teeth, used primarily for rasping rocks and sand — and more than capable of eating anything imaginable. During his first attempt at riding a sandworm in Dune, Paul Atreides notes, "Its mouth was some eighty meters in diameter ... crystal teeth with the curved shape of crysknives glinting around the rim . . . the bellows breath of cinnamon, subtle aldehydes ... acids ..."
Sandworms grow to hundreds of meters in length, with specimens observed over 400 meters long and 40 meters in diameter, although Paul becomes a sandrider by summoning a worm that "appeared to be" around half a league (2,778 meters) or more in length. These gigantic worms burrow deep in the ground and travel swiftly; "most of the sand on Arrakis is credited to sandworm action."
Sandworms are described as "incredibly tough" by Liet-Kynes, who further notes that "high voltage electrical shock applied separately to each ring segment" is the only known way to kill and preserve them; atomics are the only explosive powerful enough to kill an entire worm, with conventional explosives being unfeasible as "each ring segment has a life of its own." Water is poisonous to the worms, but is in too short supply on Arrakis to be of use against any but the smallest of them.
Herbert notes in Dune that microscopic creatures called sand plankton feed upon traces of melange scattered by sandworms on the Arrakeen sands. The sand plankton are food for the giant sandworms, but also grow and burrow to become what the Fremen call Little Makers, "the half-plant-half-animal deep-sand vector of the Arrakis sandworm.
Their leathery remains previously having "been ascribed to a fictional "sandtrout" in Fremen folk stories," Imperial Planetologist Pardot Kynes had discovered the Little Makers during his ecological investigations of the planet. Kynes determines that these "sandtrout" block off water "into fertile pockets within the porous lower strata below the 280° (absolute) line," and Alia Atreides notes in Children of Dune that the "sandtrout, when linked edge to edge against the planet's bedrock, formed living cisterns." The Fremen themselves protect their water supplies with "predator fish" who attack invading sandtrout. Sandtrout can be lured by small traces of water, and Fremen children catch and play with them; smoothing one over the hand forms a "living glove" until the creature is repelled by something in the "blood's water" and falls off.
The sandtrout ... was introduced here from some other place. This was a wet planet then. They proliferated beyond the capability of existing ecosystems to deal with them. Sandtrout encysted the available free water, made this a desert planet ... and they did it to survive. In a planet sufficiently dry, they could move to their sandworm phase. — Leto Atreides II, Children of Dune
The sandtrout are described as "flat and leathery" in Children of Dune, with Leto Atreides II noting that they are "roughly diamond-shaped" with "no head, no extremities, no eyes" and "coarse interlacings of extruded cilia." They can find water unerringly, and squeezing the sandtrout yields a "sweet green syrup." When water is flooded into the sandtrout's excretions, a pre-spice mass is formed; at this "stage of fungusoid wild growth," gases are produced which result in "a characteristic 'blow,' exchanging the material from deep underground for the matter on the surface above it." After exposure to sun and air, this mass becomes melange.
Kynes' "water stealers" die "by the millions in each spice blow," and may be killed by even a "five-degree change in temperature." He notes that "the few survivors entered a semidormant cyst-hibernation to emerge in six years as small (about three meters long) sandworms." A small number of these then emerge into maturity as giant sandworms, to whom water is poisonous. A "stunted worm" is a "primitive form ... that reaches a length of only about nine meters." Their drowning by the Fremen makes them expel the awareness-spectrum narcotic known as the Water of Life.
While sandworms are capable of eating humans, the latter do contain a level of water beyond the preferred tolerances of the worms. They routinely devour melange-harvesting equipment — mistaking the mechanical rhythm for prey — but they only seem to derive actual nutrition from sand plankton and smaller sandworms. Sandworms will not attack sand trout.
In Children of Dune, Leto II's prescient visions illuminate his Golden Path, his plan for the continued survival of mankind and the sandworms. After consuming massive amounts of spice, he allows many sandtrout to cover his body, the concentration of spice in his blood fooling the creatures:
The sandtrout squirmed on his hand, elongating, stretching ... becoming thin, covering more and more of his hand. No sandtrout had ever before encountered a hand such as this one, every cell supersaturated with spice ... Delicately Leto adjusted his enzyme balance ... The knowledge from those uncounted lifetimes which blended themselves within him provided the certainty through which he chose the precise adjustments, staving off the death from an overdose which would engulf him if he relaxed his watchfulness for only a heartbeat. And at the same time he blended himself with the sandtrout, feeding on it, feeding it, learning it ... He located another, placed it over the first one ... Their cilia locked and they became a single membrane which enclosed him to the elbow ... This was no longer sandtrout; it was tougher, stronger. And it would grow stronger and stronger ... With a terrible singleness of concentration he achieved the union of his new skin with his body, preventing rejection ... They were all over his body now. He could feel the pulse of his blood against the living membrane ... My skin is not my own. — Children of Dune
This layer gives Leto tremendous strength, speed and protection from mature sandworms, who mistake his sandtrout-covered body for a lethal mass of water. He calls it a "living, self-repairing stillsuit of a sandtrout membrane," and soon notes that he is "no longer human."
Gradually over the next 3,500 years, Leto not only survives but is transformed into a hybrid of human and giant sandworm, By the time of God Emperor of Dune he has exterminated all other sandworms, and his own transformation has modified his component sandtrout. with all the strengths and sensitivies of the species. When he allows himself to be assassinated, the sandtrout release themselves to begin the sandworm life cycle anew; subsequent offspring are tougher and more adaptable than their predecessors, allowing them to ultimately be more easily settled on other worlds and thus ensuring the survival of the sandworm species.
In Dune, the desert of Arrakis is the only known source of the spice melange, the most essential and valuable commodity in the universe. Melange is a geriatric drug that gives the user a longer lifespan, greater vitality, and heightened awareness; it can also unlock prescience in some subjects, depending upon the dosage and the consumer's physiology. This prescience-enhancing property makes interstellar travel possible. Melange comes with a steep price however: it is addictive, and withdrawal is a fatal process.
A byproduct of the sandworm life cycle, sandtrout excretions exposed to water become a pre-spice mass, which is then brought to the surface by a buildup of gases and develops into melange through exposure to sun and air. Liet-Kynes describes such a "spice blow" in Dune:
Then he heard the sand rumbling. Every Fremen knew the sound, could distinguish it immediately from the noises of worms or other desert life. Somewhere beneath him, the pre-spice mass had accumulated enough water and organic matter from the little makers, had reached the critical stage of wild growth. A gigantic bubble of carbon dioxide was forming deep in the sand, heaving upward in an enormous "blow" with a dust whirlpool at its center. It would exchange what had been formed deep in the sand for whatever lay on the surface.
Collecting the melange is hazardous in the extreme, since rhythmic activity on the desert surface of Arrakis attracts the territorial worms, which are capable of swallowing even the largest mining equipment whole. Harvesting is carried out by a gigantic machine called a Harvester, which is carried to and from a spice blow by an enlarged version of the ornithopter known as a Carry-All. The Harvester on the ground has three scouting ornithopters patrolling around it watching for wormsign — the motions of sand indicating that a worm is coming. Melange is collected from the open sand until a worm is close, at which time the Carry-All lifts the Harvester to safety. The Fremen, who base their entire industry around the sale of spice and the manufacture of materials out of spice, have learned to co-exist with the sandworms in the desert and harvest the spice manually for their own use and for smuggling off-planet.
Later in the series, an artificial method of producing the spice is discovered by the Bene Tleilax, who develop in secret the technology to produce melange in axlotl tanks. Still, the technology is not fully successful in pushing natural melange out of the marketplace.
Due to the value of melange, attempts have been made to transplant production onto other planets. However, placing either adult sandworms (often smuggled with funds going to the Fremen) or sandtrout into existing deserts always met with failure. The large salt flats of Arrakis indicate that it was not always a desert, but once had oceans. As spice production relies on the existence of a complete sandworm cycle, transplanting adult worms prevents the spice cycle from beginning anew with sandtrout, and transplanting sandtrout alone into existing desert denies them the necessary water to begin the cycle. Thus, placing sandtrout on a water-rich planet would allow them to start the complete spice cycle, at the cost of turning the planet into a desert, another Dune.
In Heretics of Dune, the Honored Matres destroy Arrakis and the Tleilaxu, in part to eliminate spice production and thus irrevocably damage the Old Empire. However, they are thwarted by the Bene Gesserit, who escape with a single sandworm. Mimicking the devolvement of the God Emperor Leto II, they submerge the worm in spice-rich water, causing it to separate into its component sandtrout. The Bene Gesserit soon use the sandtrout to terraform their own planet Chapterhouse into another Dune, and send countless others out into space to colonize other planets.
Sandworms, due to their size and territorial nature, can be extremely dangerous even to Fremen. Sandworms are attracted to and maddened by the presence of Holtzman force fields used as personal defense shields. Due to this, these force fields have very limited utility to soldiers on Arrakis.
The Fremen manage to develop a unique relationship with the sandworms. They learn to avoid most worm attacks by mimicking the motions of desert animals and moving with the natural sounds of the desert, rather than the rhythmic vibration patterns that attract worms. However, they also develop a device known as a thumper with the express purpose of generating a rhythmic vibration to attract a sandworm. This can be used either as a diversion, or to summon a worm for the Fremen to ride.
The Fremen secretly master a way to ride sandworms for transportation across the open desert. First a worm is summoned with a thumper, the worm-rider then runs alongside it and catches one of the ring-segments with special maker hooks. The hooks are used to pry up the front of the segment, exposing the soft inner-tissue to abrasive sand. To avoid irritation, the worm will rotate this to the top of its body, carrying the rider with it. The worm will then safely remain above the surface until the hooks are released. Other Fremen may then plant additional hooks for steering, or act as "beaters", hitting the worm's tail to make it increase speed. A worm can be ridden for several hundred miles and for about half of a day, at which point it will become exhausted and sit on the open desert until the hooks are released, when they will burrow back down to rest. The worm-riding ritual is used as a coming-of-age ritual among the Fremen. Worm-riding is then used by Paul-Muad'Dib during the Battle of Arrakeen for troop transport into the city after using atomic weapons to blow a hole in the Shield Wall.
After the reign of Leto II sandworms become un-rideable, for reasons elaborated below. The one remarkable exception is a young girl named Sheeana, an Atreides-descendant who possesses a unique ability to control the worms and safely move around them.
Sandworms possess remarkable teeth inside their maws. Fremen extract these teeth and use them as knives. This special type of knife is known as a crysknife. They are usually about as long as a standard kindjal. There are two types, fixed and unfixed. Unfixed knives are raw sandworm teeth used as weapons. They need to be stored in close proximity to a magnetic field produced by the human heart or they will become brittle within a short period of time, ultimately disintegrating. This is the source of one traditional Fremen battlecry, "May your blade chip and shatter!", stating that a Fremen always keeps his weapon close to hand, while many of their enemies are rarely prepared to fight and their weapons – or at least their skills in their use – are weak. Fixed crysknives are put through chemical processes to keep them permanently intact.
Fremen tradition dictates that once a crysknife is drawn, it must not be sheathed until it has drawn blood. The Fremen "legend," as described in the 2003 Children of Dune miniseries, is that the crysknife dissolves when its owner has died.
In Children of Dune, Leto II initially avoids the high concentrations of melange which had given his father Paul complete prescience, and had precipitated his aunt Alia's descent into Abomination. As part of a plot set in motion by Alia, Leto is eventually kidnapped and forced to consume large amounts of the spice; this "supersaturation" allows him to merge with sandtrout and ultimately become a human-sandworm hybrid.
Over 3,500 years the bulk of Leto's body is gradually transformed into that of a worm, and he is elevated to the role of the pharaonic God Emperor of the universe. In God Emperor of Dune he allows himself to be assassinated by Atreides descendant Siona Atreides and a ghola of Duncan Idaho. Cast into the Idaho River, his worm body separates into its component sandtrout, which immediately begin to undo the terraforming of Arrakis. Each one, according to Leto, carries in it a tiny pearl of his consciousness, trapped forever in an unending prescient dream. With the increased amount of neural-ganglia and human-like adaptiveness the worms become too irritable to ride, but are also finally able to be transplanted to a variety of worlds across the universe. Over the next 1500 years Arrakis, now called Rakis, is returned to a desert and the worms thrive once more.
Bene Gesserit Mother Superior Taraza becomes aware in Heretics of Dune that humanity is being limited by the prescient dream of Leto, and controlled by him through his worm remnants. She engineers the destruction of Rakis by the Honored Matres to free humanity, leaving one remaining worm to start the cycle anew. Taraza is killed; her successor Darwi Odrade takes the worm to Chapterhouse. She submerges it in a spice bath to generate sandtrout, with the goal of populating Chapterhouse, and later other planets, with new worms and infinite potential for gathering spice.
Besides film and television adaptations, the Dune franchise has been adapted into a series of computer and video games in which sandworms play a part.
Towards the end of the real-time strategy game Emperor: Battle for Dune, it is revealed that both the Tleilaxu and the Spacing Guild have been secretly experimenting with the sandworms of Arrakis in a remote research facility in the desert as the three great Houses of the Landsraad, the Atreides, Ordos and Harkonnen are busy waging the War of Assassins amongst each other. It appears that the Tleilaxu have discovered the link between the Spice Melange and the sandworms as mentioned above. They plot to seize the Golden Lion Throne by breeding a man-worm, known as the Emperor Worm, and then fusing it with the Water of Life, mercilessly taken from the Lady Elara — who was held prisoner by the Reverend Mother (in truth a Tleilaxu Face Dancer) since the beginning of the game — giving the Worm almost god-like powers.
All three Houses fight against the Guild in a race against time to destroy the Emperor Worm before it awakens, with a different ending for each House depicting their units destroying the Worm. One such ending reveals that, from the wreckage of the Emperor Worm's scaffold, red eyes are glowing in the dark, which perhaps suggests that the Worm survives. Should the player fail to defeat the Emperor Worm, then it becomes crowned as the new leader of the Empire of Man.