It is written that at the bottom of the Great Void Between the Worlds their is an enormous hole. This hole is the mouth of a great dragon whose very bowels are a series of fiery realms that serve to imprison its inhabitants. This is the Pit - the abode of demons, devils, and other creatures that once sought to dethrone the God of Law. Now they are content to gnaw at the fabric of Creation, to unmake reality. In so doing they hope to end the torment that has become so entwined with their very being.
The Horned One is one such individual. He is one of the most powerful demons known to the mortal realm. Human scholars interested in such things have termed him a Great King of Hell, likening him to Armadeus, Azazel, and others of that ilk. This of course is to apply a lawful construct onto the very essence of chaos itself, but it is a useful shorthand.
Descriptions of the Horned One's appearance vary greatly, and some believe this is because he is able to subtly shift his form. He is always described as a tall, male figure with large horns or antlers. Sometimes he possess the head of a goat, sometimes a handsome man, still others an aged crone - making his form strangely androgynous despite his otherwise masculine features. He is usually either naked or wrapped in silk cloth, though this never covers his genitals. His skin is either silvery or black, but is always cold and shines like steel. His body hair - or fur as the case may be - is always thick and hard as copper wire, even though it shifts in the wind and to the touch of his own hand as though it was quite fine.
The Horned One is said to have complete control over human sexuality and to know all Natural Sciences. It is for these reasons that sorcerers are most likely to summon him. He will cause any person to fall in lust with any other, and he is known to aid desperate men and women in fulfilling all manner of perversions and turpitudes otherwise impossible in a Lawful universe. He will also instruct witches and wizards in the construction of tinctures, tonics, and toxins of various sorts. The price for these services goes beyond the summoner's soul, as they must also yield to the beast's insatiable sexual desires. Unfortunately for many, this part of the bargain is revealed all too late.
While more academic magic users call on him, the Horned One is most firmly associated with witches. He is also called the Man of the Mass, and it is he, or more likely one of his incorporeal avatars, who presides over the terrible rites common in the Anti-Church. His handmaidens, blind maenads said to have been mortal servants who knew his touch too many times to retain any semblance of sanity, officiate dark rituals in which infants are rolled in dough and cooked in large ovens before acting as a eucharist for a diabolically ecstatic crowd. Anti-Bishops preside over strange un-marriages to corpses and he-goats. It is these rituals that give Anti-Clerics and Witches their unholy powers.
Perhaps the most common ritual of all is sexual union, either willing or unwilling, with the Horned One himself. This often occurs at the apex of Black Masses or after the demon-lord has rendered specific services for the sacrifice. He is fond of changing his appearance in the middle of intercourse, shifting from a beautiful man to a hideous he-goat. The Horned One cares not for age or gender. He will copulate with any and all put before him, and his ice-cold semen has been known to impregnate men with his vile spawn. Witch hunters will often torture pot-bellied men under the assumption that they have known the Horned One's touch.
These pregnancies are not of the sort normal to human beings, as one might suspect. The Horned One's penis is trifurcate, capable of penetrating three separate orifices or three separate people at one time. Any orifice thus penetrated will produce 1d3 Devil-Men in nine months time.** These are always expelled in the most violent and gruesome way possible, but this only rarely ends in the death of the victim. Instead, they are usually hideously scarred and disfigured for the rest of their miserable lives.
The Horned One has many minions in the mortal realm. His most common servitors are humans, but Devil-Men and a number of Beastmen also call him master. He is the demon prince with the most purchase in this reality, but this was not always so...
* While these are most commonly demon princes, there are also numerous "individual" demons of lesser power. These are commonly employed as familiars or guardians by foolish magic users who think they can control such forces.
** It is rumored that other demon lords can create Devil-Men by different means.