The Barabbi are supposedly named for Barabbas, the murderer set free in place of Christ, the barabbi began along a different Path but then converted to the Nephandic cause. Traitors to their original sects, these people have had their souls literally turned inside out in the Cauls: metaphysical inversion chambers in which an Awakened Avatar chooses to damn itself and be born again through the Gate of Dark Rebirth. Now, they embody the worst qualities of their former sects... and probably still belong to those groups, tempting their colleagues toward atrocious deeds and taking their philosophies to the sickest possible extremes.
