Brotherhood of Skulls has existed since antediluvian times. One of its original names was The Manhunters or The Fishers of Men or Manfishers.
From the very beginning through to now they have operated continuously. Their uniform has always been black, their symbol always a silver skull.
They believe in physical immortality. Their means of achieving it, received direct from the devil god that founded them, are as follows:
Perverted sex
Sex magick
The ritual of the Smothering Air
The binding of demons
The trafficking with "unclean spirits", "demons of air and darkness" and "devils"
Human sacrifice of the most grisly sort including exsanguination, ripping the living hearts out of victims, sacrifice of children, mass murder, mass cremation for homeopathic ie ritual magic purposes and skinning virgins alive
At different times and in different places they have arrived to establish versions of their order:
"Atlantis"- the world before the Flood - the Order of GIR.RA.UD
"Headhunters" amongst the debased of the "Children of Noah"
Sumerian and Semitic Lillith Cult
Temple of Cthon
Cult of the Nameless One
Black Order of the Book of Skulls, Ancient Britain
Etruscan Cult of Orc
Roman Dis Pater sect
Priesthood and Scribes of Rahan Capuac
Witch Cult
Aztec priesthood of Tezcatlipoca
Jesuits
Illuminati
Skull and Bones (and related Phi Beta Kappa groups)
Nazi Germany - the SS
Hell's Angels bikie movement
Vampire the Masquerade / Goth subculture controllers
At each point, the Black Order or Brotherhood of Skulls has never numbered many members- a tiny handful in fact. But their effects have always been colossal since they are communicating the literal processes of the ancient "gods", never meant for human use or human life.