Rancors, sizable carnivorous reptiles possessing a degree of sentience, were native to the planet of Dathomir. However, they also existed on Felucia, Tatooine, and Koboh after being introduced to these worlds. Their frequent employment as combatants across the galaxy gave them a reputation as unthinking, savage beasts, yet they demonstrated the capacity for training and strong bonds with their handlers and associates.
Rancors, standing at approximately five meters in height, presented an imposing figure. Their characteristics included lengthy arms, clawed digits, massive jaws filled with teeth, and armored hides capable of resisting significant blaster weapon strikes. These features made them fearsome predators. Despite their notorious and frequently intimidating displays when provoked, they were not inherently malevolent toward sentient beings. A subspecies known as the jungle rancor thrived on Felucia. Rage rancors surpassed other rancor subspecies in height and exhibited an even more ferocious disposition. Shadow rancors, so named because of their darker hides, were infamous for their destructive tendencies. The accepted plural term for a group of rancors in Galactic Basic Standard was a crash. Rancors possessed red blood; when the Sith Lord Darth Vader inflicted a wound on a rancor that had been augmented through the cyberanimate program, blood issued forth instead of the wound undergoing cauterization.
Rancors lived within a social structure defined by a hierarchy, in which an alpha individual held dominance over the others until defeated. In their essence, these massive and intimidating creatures were actually quite gentle. The Witches of Dathomir eventually domesticated wild rancors through the use of witchcraft and dark force magick. However, they remained powerful animals with a short temper, easily incited to violence. Although frequently raised for combat purposes, rancors could develop strong affections for their owners and handlers if they received proper training and socialization. Young rancors displayed high energy levels and a blissful ignorance of their own strength, often causing unintentional harm. However, they could be easily pacified with a chewing bone or a favored toy. Once taught basic obedience, young rancors could become calm and develop into gentle, protective companions. Scavenging birds commonly cleaned the mouths and teeth of rancors, with the giants patiently awaiting the avian cleaners with open mouths. Yet, when it came to larger creatures, rancors would eat anything they could swallow.
The Fromprath's arrival on Dathomir led to the exploitation of the planet's natural resources, which motivated the Nightsisters to forge a symbiotic "alliance" with the native rancors as a means of expelling the colonizers. The Hutt Clan utilized rancors as mounts for their enforcers, such as Gamorrean Warriors. During the High Republic Era, the Jedi Order and the Hutts were compelled to ally against the Drengir, leading the Jedi of the Galactic Frontier to ride rancors into battle alongside Hutt forces. In response to the slaughter on Daivak, Jedi Master Avar Kriss and Jedi Knight Terec rode rancors into battle against the Drengir, while Terec's bond-twin (and fellow Knight) Ceret and Hutt leader Myarga Anjiliac Atirue accompanied them on speeders. The Drengir began to overwhelm their adversaries, with one extending its tentacle-like vines into the mouth and nostrils of Kriss' rancor, forcing her to dismount as the beast succumbed to the Drengir infection.
To Kriss' dismay, Myarga swiftly executed the rancor when it began to turn against them. Following the Drengir's sudden screams, the battle resumed, with Jedi Knight Keeve Trennis infiltrating the species' root-mind. After discovering the location of the Great Progenitor on the planet Mulita, Terec's rancor seized one of the botanical monsters. During the assault on Mulita, the Jedi and Hutts launched a massive strike against the Drengir, with Trandoshan Jedi Master Sskeer riding a rancor into battle. Despite Sskeer's attempts to sever the vines, his rancor was subdued by the Drengir's tendrils. Ultimately, however, the battle concluded in victory for the Jedi and Hutts, as the Great Progenitor was forced back into slumber.
The jungle rancor subspecies inhabited the world of Felucia. Following the destruction of the Felucia Medical Station HCTFF2, Jedi General Obi-Wan Kenobi, Jedi General Anakin Skywalker, and Jedi Commander Ahsoka Tano observed a group of these rancors on the planet. They took care not to frighten the creatures, as the jungle rancors and the native Felucian farmers generally lived in harmony.
After the rise of the Galactic Empire, Clone Force 99 was contracted by Cid to rescue Muchi, a young rancor on Ord Mantell, although they were unaware of her species. Omega released Muchi to aid the squad and some slaves in escaping from a group of Zygerrian enslavers, and Echo expressed surprise at discovering that Muchi was the rancor, not one of the slaves.
In 9 BBY, a rancor caused the deaths of several prospectors on the planet Koboh. Cal Kestis, a Jedi Knight, eventually killed the rancor when he was dispatched to investigate the prospectors' disappearance. Later, he discovered another rancor in the aptly named Phon'Qi Caverns, which had apparently resided there for some time, preying on those unfortunate enough to cross its path, including the Bedlam Raiders. Cal displayed noticeable disbelief after killing the second rancor.
Following the death of a Trandoshan enhanced by the Cylo Directive's cyberanimate program at the hands of Darth Vader, the Sith Lord, the Cylo Directive implanted the cyberanimate into a rancor instead. The system was directly connected to the creature's brain in an attempt to bypass any vulnerabilities it might possess. Specifically, the rancor was outfitted with neural dampeners to eliminate pain, adrenal stimulants, and a plate-reinforced thorax. In the events leading up to the hijacking of the Executor, by which time the rancor was the most recent creation of the labs, Doctor Tulon Voidgazer unleashed the cyborg creature against Vader in what she termed experiment 428. The rancor approached Vader via vector e on her order and did not react when Vader severed part of its hand, due to its neural dampeners, before charging at Vader in a rage upon being stimulated by its adrenal stimulants. While Voidgazer considered it an uninspired response, she was pleased by the thorax's resistance to Vader's Force choke attack. Nevertheless, once she explained the system, Vader defeated the beast by impaling its brain with his lightsaber, killing it.
Jabba the Hutt kept a massive rancor named Pateesa as a pet in a dimly lit chamber beneath his palace court, where he would feed his enemies or anyone who displeased him. During the mission to rescue Han Solo, Jabba sent the young Jedi Knight Luke Skywalker into the pit. After the terrifying creature devoured one of Jabba's Gamorrean guards, the young Jedi defeated the rancor, shocking all who witnessed it. Malakili, Pateesa's human handler, mourned the rancor's death, while an enraged Jabba ordered the public execution of the Jedi and his companions.
In 9 ABY, the Hutts known as The Twins presented a rancor to Daimyo Boba Fett on Tatooine as both tribute and an apology for dispatching the Wookiee gladiator Krrsantan to assassinate Fett. The rancor was fitted with blinders, which its keeper explained was due to the tendency of rancors to "imprint" on the first human they saw. Boba removed the rancor's blinders and began to form a bond with his new companion, requesting the rancor keeper to teach him to ride it as the Witches of Dathomir had. When the Pyke Syndicate began to utilize Tatooine as part of their spice trade, Fett convened with Mos Espa's criminal leaders at his palace in an attempt to persuade them to join him against the Pykes. During the meeting, Fett's guests expressed surprise at the rancor positioned just below them.
During the battle in Mos Espa, Fett and his allies found themselves outnumbered by the Pykes, a situation exacerbated by the Pykes' deployment of Scorpenek droids equipped with deflector shields, rendering their weapons largely ineffective. To redress the imbalance, Fett withdrew from the battle and returned mounted on his rancor, leveraging his bond with the creature and its species' reputation to instill fear within the Pyke forces. The rancor's arrival altered the course of the battle, with the creature demonstrating, interestingly, a superior combat style compared to the Scorpenek units.
When Cad Bane, a bounty hunter and Fett's former mentor and rival working for the Pykes, arrived, the rancor was frightened away by Bane's flamethrower, causing Fett to fall from its back. Without Fett to control it, the rancor began to wreak havoc on the city. Din Djarin, a Mandalorian bounty hunter recruited by Fett, confronted the rancor and narrowly escaped death. However, before the rancor could kill him, Grogu, a Force-sensitive child of Yoda's race under Djarin's care, intervened and used the Force to calm the beast and lull it to sleep, an act that also caused Grogu to fall asleep due to the exertion.
Between 9 ABY and 34 ABY, the Trandoshan Hunter Charr possessed a set of rancor bones, which he wore during the Hunters of the Outer Rim tournament at the Grand Arena on the planet Vespaara.
The creators of the rancor in Return of the Jedi described its concept as "a cross between a bear and a potato." George Lucas instructed that the rancor be "the best" Godzilla-like monster ever made, as recalled by Phil Tippett. Similar to Godzilla, the initial plan was for the rancor to be portrayed by an actor in a suit. The costume required two actors: one to control an arm, and the other to control the other arm and the rancor's body. Despite scheduled shooting to commence in a matter of days, the costume tests yielded unsatisfactory results. Visual effects supervisor Dennis Muren believed the team was progressing toward a satisfactory final product with the suit, especially considering lighting, cutting, and camera angles. However, George Lucas himself ultimately determined that the design was not effective and would not be included in the final film.
After the abandonment of plans to have suit actors portray the rancor, Tippett and his team—as Tim Rose, a puppeteer, recounted to Star Wars Insider—intended to use go-motion, a form of stop motion animation that produces smoother results than traditional stop motion. This plan was changed after Tippett saw Rose's work on Ackbar. Furthermore, as noted by Insider in an interview with Muren and fellow Return of the Jedi visual effects supervisor Ken Ralston, there was insufficient time in production to film the rancor using go-motion or stop motion. Ultimately, using a puppet proved to be a simpler solution that aligned with the time constraints. These interviews were published in Star Wars Insider 222 as "Inside the Mind of the Puppetmaster" and "Together Again, Huh?," respectively. In his interview, Muren recalled that the team had explored alternative methods for realizing the rancor before settling on rod puppetry. Rose stated that his work on Admiral Gial Ackbar—whose head Rose puppeteered in close-up shots for the film—and Tippett's enjoyment of it "influenced" Tippett's decision to switch to puppetry.
Ultimately, the rancor was created as a rod-operated puppet. Rose operated the puppet, specifically describing the rancor as an example of Bunraku rod puppetry. It was filmed using a high-speed camera to slow down its movements, creating the illusion of a much larger creature. In an effort to experiment with any method that could make the rancor "more real" and authentic, in Muren's words, the team aimed to convey the creature's scale and fluidity on screen. To that end, in addition to filming it at high speeds, the crew filmed the puppet in reverse—with Tippett personally moving the rancor puppet backwards—and at extremely low speeds. One shot required at least ninety takes over approximately ninety minutes, according to Muren, to capture all the "little sequences of frames." Throughout the process, the crew was aware of the intended cuts in the scene and simply had to integrate them into the overall edit. Overall, Muren described the experience as them "just [shaking] it up."
Muren reflected that, had the puppet not been successful, the crew would have been forced to rely on the time-consuming process of stop motion. While Muren credited Tippett for the rancor's strong design, he admitted to Insider that, whenever he watches the rancor pit sequence, he only sees the effort invested in it. As a result, he was surprised by the scene's popularity among fans.