Brotherhood of Bones (BoB) was a secret society of necromancers and followers of purest evil led by Goshnar. They were vanquished long ago by their arch-enemies, the Nightmare Knights.
The Brotherhood of Bones came to Darama fleeing some war on the continent. They corrupted the settlers of the Thaian colony with ease. That was the beginning of undead-city Drefia. When the Djinns destroyed the better part of the unholy town in their wrath, the Brotherhood hid underground.