The B'omarr are the monks who built the massive monastery fortress Jabba the Hutt occupies as his palace. They are spider-droids that carry around a nutrient-globe containing a living, sentient brain. These brains are all that remain of the enlightened monks.
There is a quest in Mos Entha concerning the B'omarr monks and a former initiate into their order.
Star Wars Lore
The B'omarr Monks were a mysterious religious order that moved to the planet Tatooine many centuries before the Battle of Yavin. They believed that cutting themselves off from all civilization and distraction was essential to their enlightenment. They built a cavernous monastery on the edge of the Dune Sea, and spent many quiet centuries in meditation.
The monks come from many species. Their minimalist views led them to sometimes go months without saying a word. Discourses and lectures were whittled down to a single word that the monks would meditate on. At a certain point in the monk's development, the lesser monks of the order assisted him with a "shedding" surgery. The body was seen as just another distraction, so it was discarded. The monk's brain was inserted into a nutrient jar, and placed on a shelf, where it would meditate and contemplate for millennia. On the offchance that an enlightened monk had some business to attend to, he used his mind to summon a mechanical spider-like apparatus, which picked up his jar, and secured it so he can become mobile. If such an enlightened monk was encountered walking the halls of the monastery, his apparatus was given a generous breadth, and was often bowed to.
Occasionally, Jabba interacted with the monks, allowing them access to prisoners they dubbed "interesting." One such event occurred when Han Solo was imprisoned following his release from carbonite, and he consented to tell his story to a young monk there.
At other times, Jabba would ask(probably with the threat of violence attached) that the monks help him "punish" certain enemies, particularly through the use of the afformentioned surgical procedure.