(the former Theology major steps in) I seem to remember that Satanism has very little to do with Satan, but rather the absense of god. That there is nothing after this, you live, have exclusive control over everything that happens to you, then you die and cease to exist.
Now if you wanna talk about Satan you have to bring in both manifestation. One is the angel Lucifer who was cast down from heaven into predition with his followers, the other is the classic goat headed/hooved demon that has some connection with Lilith the true first woman (who was cast from the Garden of Eden because she refused to lay beneath Adam....YOU GO GIRL!) who is apparently the mother of all demons. There were so many damn rewrites we'll never really know the real story. I mean their are passages in the bible that claim that Lucifer WAS the serpent that offered the fruit of knowledge and later was also somehow the rebellious angel that was banned from heaven.
The second variation with the goat parts was just a manifestation concocted by early Christians trying to demonize the old faiths of the Greek empire. The god Pan, the quintessential "party god" into hedonism, drinking, permiscuity and any other guilty pleasure was easily sculpted into a demon of sin to sway the faithful greeks. Ever noticed they both got the half goat/half man thing going on?
Christians also clumped Wicca, Paeganism, the Druids and early Gaelic faiths in with the Satanist propoganda with their "frightening" beliefs oriented around earth spirits or faeries and elves. By all accounts the Catholic church created the demonized modern stereotypes that see Wiccans, Paegans and Satanists as evil and immoral.....
"What? Something different?? EVIIIIIIL!!!!"
Personally I think the greeks had the right idea. Hades wasnt being punished, it was just his job. Zeus ruled the sky, Poseiden ruled the Sea and Hades ruled the Underworld. Of course Hades was more of a Grim Reaper type character than a Devil. The realm of Hades can be compared to purgatory or limbo, a halfway point between worlds. The realm of Tartarus was the greek version of hell, a firely pit of eternal suffering controlled by the Titans.
My favorite Hell though is the Chinese Thousand Hells controlled by King Yama (also appears in the Hindu faith) which combines the aspects of Damnation and Reincarnation. There is a level for every type of sin, and depending how evil you were determines how long your torment will last. After your "sentence" is served, you're soul is cleansed and sent back to the living world to try again, in a lower state of existence than before of course. (A rich man who sinned would return as a beggar and so forth)
Funny side note I realized. One area of the world the Christians had the hardest time converting were the Eskimos, for one reason. When threatened with an eternity burning in hellfire, you gotta realize, its so cold an idea like that was actually appealing! They should have gone with the depiction of the lowest level of hell in Dantes Inferno, where you're frozen up to your head in ice....