These individuals were the spiritual leaders of the Felucian race and were capable of using the Force to defend and heal their comrades or surround themselves in a defensive aura that was harmful to attackers. They ensured that any of their brethren who fall to the Dark Side were immediately executed in the Ancient Abyss - the resting place of one of the largest sarlaccs in the galaxy[source?], for they knew that the presence of a strong dark Force-user would corrupt not only the flora and fauna of Felucia, but also the planet itself. For this reason those Felucians who showed interest and exceptional aptitude in the Force were usually trained in ways of shamanism whether they wanted to or not, because shamans could not risk a potential powerful Force-user growing up among them without receiving a proper training to resist the lure of the dark side.
When pressed into battle, they were capable of defending themselves but often attempted to flee such engagements in order to use a combination of Force talents and their innate camouflage abilities to seemingly disappear to a safer distance from their enemies.
Numerous shamans were present on Felucia to defend Jedi Master Shaak Ti from Darth Vader's assassin. However, many were killed in this attempt and when Shaak Ti died in the Ancient Abyss, a Shaman inspected the sarlacc to determine if she had survived. Once it was confirmed she died, the Felucians allowed Marek to leave their world.
Sometime later, Shaak Ti's Padawan Maris Brood began to fall to the dark side of the Force which was corrupting the Felucians as well. When Marek returned to free Bail Prestor Organa, he had to fight numerous shamans once again on that planet.