Jabba's rancor was a rancor given to Jabba Desilijic Tiure kept beneath a trapdoor in his chamber. He was fond of dropping people into the rancor's pit and watching them be eaten.
"The Keepers forced Jabba's rancor into a dungeon where it could barely move. It was half-starved. Though I didn't have a choice, I'm still sorry I had to kill it."
Jabba's rancor with a large bone caught in his mouth
The rancor was being transported from the Tarsunt system by Grizzid for a Bothan merchant named Grendu, when it broke out, killing Grizzid and his crew, and causing the ship to crash on Tatooine. A JawaSandcrawler captain named Tteel Kkak discovered the wreckage and informed Jabba's servants Bib Fortuna and Bidlo Kwerve. They presented it to Jabba as a birthday present. Fortuna was rewarded by being made Jabba's Majordomo, while Kwerve was fed to the rancor.
Malakili was bought from the Circus Horrificus in order to care for the rancor. He became very emotionally attached to it. While he took the rancor for a walk in the desert, it saved him from a small gang of Sand people. Jabba enjoyed pitting the rancor against other exotic monsters for his amusement. It always won, but was seriously wounded by three Caridan combat arachnids. When Malakili discovered that Jabba planned to pit the rancor against a krayt dragon, which would surely kill it, he made plans to betray Jabba to LadyValarian and escape Tatooine with the rancor.
Jabba frequently used his rancor as an amusing form of execution. Oola the Twi'lek dancing girl was dropped in for resisting Jabba. Later, Jabba used it against Luke Skywalker, accidentally dropping a Gamorrean guard named Jubnuk in as well. The rancor ate Jubnuk, but Skywalker tricked him and crushed him under a heavy portcullis, piercing and crushing its skull, killing it.
Warning: The following section is ambiguously canon. It contains information that originates in a source, possibly unlicensed, that has not been deemed definitively canon.
Jubnuk was later cut out of the rancor's stomach, still alive due to the lucky talisman he found inside the stomach.[2]
Ambiguously canon information ends here.
Later, Luke stated that he had another reason for killing him, other than defending himself. The rancor was so abused and mistreated that rehabilitation for him would have been impossible, and Luke believed that it would be best to put the poor creature out of his misery.
Even two decades after the fact, Luke expressed that it was an unfortunate shame that he had to kill the rancor. He felt that as a species, they were such fine creatures.[3]
An image often mistaken to be the rancor battling a krayt dragon is, in reality, a joke from the crew of ILM. They placed a model of one of the dragons from the film Dragonslayer in the arms of the model of the rancor and took a picture. The picture was included in the book Star Wars: Chronicles. A creature based on the appearance of this dragon appears in one of Jabba's monster pens in Inside the Worlds of Star Wars Trilogy.
The rancor was originally supposed to be a man in a suit, but the results weren't satisfyingly realistic, so it was filmed in the form of a puppet.