Balphomael, the Horned Darkness, is a daemonic power that has seemed to lurk in the shadows of the Calixis Sector since it was founded, and is doubtless far older than this. It is the master of its own cult, the Brotherhood of the Horned Darkness. Over the years the Inquisition has acquired considerable lore and anecdotal evidence about this being whose power is at least that of a daemon prince, if not considerably greater. Seemingly owing no direct fealty or allegiance to any other of its kind, it has the characteristics and nature of a power broker. It is a being who demands worship and obeisance and sacrifice, who in return grants patronage and power.
Legends and scraps of lore describe Balphomael as a towering figure of unholy fire and billowing darkness, a horned shadow that can be summoned from a bonfire piled high with burning hearts given in offering. The testimony of cult members brought to question by the Holy Ordos claims that the daemon may also take the shape of a saturnine man or striking woman of imperious manner---a dealmaker whose honeyed tongue might corrupt a saint, but whose eyes burn like embers and whose shadow is cast in the terrible flickering shape of its true nature. The daemon is a powerful and dangerous entity, and one that cannot be commanded or controlled, by even the most powerful sorcerer. Some scholars within the Ordo Malleus speculate that its “appearances” in corporeal reality (including on one occasion when a powerful avatar of the beast was battled by the Holy Ordos and the Grey Knights) are actually little more than warp-projections, the meanest portion of a far greater whole that coils in the empyrean beyond.