A rancor under the care of Boba Fett was a rancor he received as a gift from the Hutts known as the Twins. As part of the Twins' tribute, a rancor keeper came to Boba Fett's Palace with the rancor to assist Fett in its care. Upon learning that the Witches of Dathomir were known to ride rancors, Fett voiced his ambition to learn the skill himself.
Around 9 ABY, the Twins, who are Hutts, presented the Daimyo Boba Fett with the rancor. The Twins' tribute included both the rancor and a rancor keeper who was to help Fett look after the creature; they both arrived at Boba Fett's Palace. The former bounty hunter was informed by the keeper that the rancor would form a bond with the first Human it saw. Fett then expressed his desire to learn how to ride the rancor, having heard of the Witches of Dathomir and their ability to do so. The keeper, curious about what Fett would name his new pet, instructed Fett to stand before the rancor as he removed its blinders. The rancor, now able to see, immediately noticed Fett and imprinted on him. Fett approached the creature with ease, petting it and discovering its favorite spot to be rubbed, near its right eye. Suddenly, 8D8 interrupted, informing them that Mayor Mok Shaiz would be unavailable for the next 20 rotations. Disappointed, the rancor watched Fett leave to confront the mayor, but the rancor keeper reassured it that Fett would return.
Fett then housed the rancor in the rancor pit located in Jabba's Palace. He employed the rancor to intimidate the crime bosses of Mos Espa when one of them made a death threat against him. Fett was able to calm his pet by feeding it, and he also threatened the other bosses by suggesting he would feed them to the rancor, implying it was hungry. During the Battle for Mos Espa, the rancor became Boba's personal mount. He used it to destroy the two Scorpenek annihilator droids unleashed by the Pyke Syndicate. Fett was knocked off the rancor during the battle, and it began to climb the city's buildings. Allied fighters attempted to shoot it, but the Force-sensitive youngling Grogu subdued the rancor and put it to sleep, ending its rampage and saving its life.
The rancor made its initial appearance in "Chapter 3: The Streets of Mos Espa," an episode of the live-action TV series The Book of Boba Fett.