Backstory: Satyrs were originally a dual-gendered race of "10% furry" (legs, tail, horns, possibly ears) goats that came in both male and female. In those days, they were called "Fauns". The Fauns believe themselves to be, at least metaphorically, the children of one of Marae's pre-demon demi-godlings, a hermaphroditic spirit in the form of an anthro-goat named Baphomet. This spirit was a god of pleasure, love, fertility, virility and carnality; as a result, the Fauns were very friendly — and very horny — individuals, constantly playing games, dancing, making music, drinking strong drink, and having sex. They were renowned for their bacchanals and orgies.
General Behaviour: Fauns live their lives to worship their guardian deity, Baphomet. They preach their religion by planting seeds of the fruit they collect; by brewing an aphrodisiac wine to be used in their parties, and by having sex. They would lure passersby with the promise of fun and pleasure by the means of a party to celebrate their god, this would often result in massive orgies since the wine in said parties happens to be their special brew of aphrodisiac wine. In their wake they would leave a few very satisfied lucky souls and small mounds of earth, where they planted new seeds to thank the nature for the gift of nourishment and pleasure.
Fauns would often be contacted by people who were infertile in hopes of healing whatever prevented them from having children. While it is true that often the Faun magic that would cure them would take the form of sexual contact with a Faun of the opposite sex, this rarely resulted in "curing" them by leaving them the mother or father of a baby Faun. Only in the most grievous cases would a Faun offer to serve as a stand-in stud or broodmare for a family in desperate hope for children.
Corruption: The corruption had a drastic effect on the Fauns' previously peaceful way of life. Because of the sexual openness of Faun culture, they were among the earliest victims of demonic influence; they literally welcomed the corruption into their souls with open arms; and before they knew it, they were being poisoned by sexual contact with the ever-insatiable corrupt legions. The denizens of Mareth owe the sudden spike in imp population to the Fauns. Eventually the females, weakened by repeated births, perished, leaving only the lust-crazed males behind. The corrupted Fauns, now called simply Satyrs, found a way to circumvent the problems that arose from the death of their females. Through the use of potent black magic, they made their seed extremely potent and able to impregnate anything that they happened to fuck, even each other.
They have abandoned their former creed of mutual pleasure to be shared amongst the willing, to instead live their lives in pursuit of excess and carnal luxury, just like the demons. When a Satyr is not seeking new mates to impregnate, they are usually drinking and polluting the nearby area with their aphrodisiac wine. They still lure passer-bys with the promise of fun and pleasure, only this time the purpose is solely to lure new victims to become the mothers of more satyrs.
Gestation and Birth: Satyr seed is infused with highly corrupt magic that enables them to literally impregnate anything. When confronted with a female or a herm of another race, the Satyr will try to fertilise them in the usual fashion; because of their tainted seed, pregnancy is all but guaranteed, and high fertility may actually result in the birth of multiple satyrs. However, so virile are satyrs that they are actually capable of anally impregnating male and neuter-gendered individuals. The thick ejaculate floods into the subject’s bowels and solidifies into a tough, leathery, egg-like mass. The interior of this egg is hollow and filled with corrupt fluids that serve as an amniotic "soup" in which a near identical clone of the Satyr "father" is grown. This infantile satyr grows inside the pseudo-womb like a regular infant would in a normal womb, with all of the usual symptoms — distended midriff, strange cravings, increased lust, sensations of movement, etc. When the infant grows large enough, the egg breaks down and the "mother" goes into labor, the liquified pseudo-womb serving as lubricant that, combined with the motions of the anal passage, brings the baby satyr into the world.
Once exposed to the outer world, the satyr's corrupted body rapidly matures until it attains full reproductive adulthood — puberty. Invariably, it will flatter its mother and offer to leave them "something to remember him by", but it retains enough civility to not become violent if they turn down this initial offer. On subsequent meetings, though, the new satyr will strive to incapacitate them and rape them into pregnancy once more.
General Behaviour (Post-Corruption): Satyrs are now highly anti-social creatures; when two satyrs meet, invariably, the stronger one will dominate and impregnate the weaker one. They still love to feast and to party, but do so in gluttonous, debauched revels. They are notorious as bandits and thieves, stealing anything they can make off with and assaulting travelers for goods and breeding partners. They are often allied with goblins, one of the few races that can stand to be around them as they are now, with the satyr trading its considerable talents as a stud in exchange for food and liquor. The only reason satyrs as a whole have not sold themselves into slavery to the goblins is because, for many, the ever-increasing supply of willing sluts doesn't outweigh the fact they can't breed any sons with goblins.