The B'omarr Order, which consisted of B'omarr monks, was a religious order that believed in isolating themselves from all physical sensation to enhance the power of their minds. To that aim, enlightened monks had their brains transplanted into nutrient-filled jars. Whenever they wanted to move, those bottled-brains used spider-like droid walkers. Older monks used four-legged walkers, but younger monks used a six-legged variant.
The order possessed multiple regeneration gems, which at the time of Jabba the Hutt were stored underground behind triple doors.
The order built monasteries in the galaxy, including a monastery on the jungle world of Teth in Wild Space. Some of their temples were taken over by smugglers, who turned them into their personal retreats. The B'omarr monks were also present on Tatooine, but Jabba the Hutt assumed control of their monastery, turning it into his personal palace. Despite that, Jabba allowed the monks to still roam around his appropriated palace, as he enjoyed the gruesome sight of them.
At some point, Jabba's cousin Crakka attempted to steal the brain of the thief Zaril from the B'omarr Order's Catacombs where the other living brains of the Order were being held. During the attempt, Crakka was detected by the Order, incurring their wrath. As Crakka made his escape, Salacious B. Crumb interrupted him, causing him to drop the brain. When confronted by Jabba, Crakka attempted to offer the secret's of Zaril's brain but the brain had already been severely damaged by the drop to yield any secrets. Seeing no use in the brain and still angered by Crakka's betrayal, Jabba did not hesitate to let the Order take their vengeance on Crakka and add her brain amongst the Order's current collection of bottled brains in the Catacombs.
In 4 ABY, B'omarr monks were present at Jabba's Palace when Jedi Knight Luke Skywalker came to rescue the Corellian smuggler Han Solo from captivity. Shortly after Jabba's death, the monks took over the palace and allowed the Whiphid bounty hunter J'Quille to join them after he found himself unable to leave the planet. By 9 ABY, Bib Fortuna had taken over the palace before he was killed by Boba Fett.
The B'omarr Order first appeared in the 1983 film Star Wars: Episode VI Return of the Jedi, in the form of brains attached to spider droids. The droids were based upon sketches by the Star Wars original trilogy concept designer Ralph McQuarrie, which later appeared in the Star Wars Legends 1995 book The Illustrated Star Wars Universe, where the B'omarr were originally identified. They were later identified in the 2015 reference book Ultimate Star Wars.