Cult of the Head
Gerbert of Aurillac was an Black Star sorcerer who broke from the Order in 999 AD when he began using an artifact called the Brazen Head. It is unknown if he constructed the device or simple discovered it somewhere. Using the vast knowledge that the Head provided, he started his own cult called the Cult of the Head. Because the head required blood sacrifice in order to work, blood sacrifices become a key tenant of the cult.
When the Catholic Church became aware of the cult’s activities, the church pursued Gerbert and his cultists relentlessly. Eventually Gerbert was killed and his surviving cult members were absorbed the Knights of the Temple. The current whereabouts of the Brazen Head is unknown.