The Mystical Brotherhood of Shomari
The Mystical Brotherhood of Shomari counts as the Possessed in technicality. After all, it pledges no allegiance to the Shadowlord or even the to demons of Chaos. Well, not necessarily, as the Witch Hunters would root them out and burn them all to hell just as fast as they would anyone else. The Shomari are a masonic group, a secret society dedicated to ancestor worship. Most of them have been persecuted for various reasons, be it race, culture, or beliefs. Some of them haven't been directly persecuted, but don't like what they see and found comfort in the shadows of society. Society has deemed them "player haters," and they have no problem with the title. They hate the way things are going, so why shouldn't they be haters? Even though the Shomari worship their ancestors, people who have encountered them have mistaken them for agents of the Shadowlord, which suits them just fine. No one needs to know what they are up to, and if someone does they have to die, preferably slowly if time allows for it. Their objective, which no one must find out, is to dominate Mordheim, then the Empire, and then the world. Yes, the entire world will pay for the pain that they have endured.
In this masonic order, there are five degrees. The fifth circle is for new initiates (bretheren) and darksouls that the Shomari decide are worthy of initiation. The fourth circle is reserved for the Gor (beastmen). As permanent outcasts in the human world, they automatically gain rank within the brotherhood. The third circle is reserved for mutants and heroes. Mutants are definitely worthy of enjoying rank, and heroes have earned the right to do so with their actions. The second circle is reserved for the Possessed, one who is advanced enough to gain direct contact and communion with the ancestors. As such, they are powerful indeed. The first and final circle is the Magister, who leads the Shomari. The Magister has been truly blessed by the ancestors and is given magical powers. It is truly an honor to become a Magister of the Shomari, as the ancestors don't bestow their powers on just anyone.