It Is Not necessarily what you may imagine...

Satanism is not one single religion. Satanism is a broad category of religions, worldviews, and literature all featuring a favorable interpretation of the figure of Satan.

Christians (and Muslims) regard their "God" as all-good and Satan as evil. But what is "good"? What is "evil"? Many of the moral values espoused in the Bible seem very strange from a modern Western point of view.

In the Garden of Eden story, Adam and Eve are punished for eating from the "tree of knowledge of good and evil." In other words, blind obedience to the Biblical "God" is considered "good," whereas independent moral judgment, based on one's own knowledge, is considered "evil." But, like many other educated people in the West today, we Satanists do not agree with this idea at all.
In the Book of Genesis, "God" seems to be outright threatened by human knowledge and achievement, both in the Garden of Eden story ("And the LORD God said, 'The man has now become like one of us, knowing good and evil. He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever.'" - Genesis 3:22) and then later in the Tower of Babel story ("But the LORD came down to see the city and the tower that the men were building. The LORD said, 'If as one people speaking the same language they have begun to do this, then nothing they plan to do will be impossible for them. Come, let us go down and confuse their language so they will not understand each other.'" - Genesis 11:5-7).

In several books of the Bible, the supposedly all-good "God" commands the Israelites to slaughter various enemy nations in their entirety, in some cases sparing only the virgin girls who are taken as slaves. Nowhere in the Bible is Satan alleged to do anything even remotely as "evil" by modern Western standards.

According to traditional Christian doctrine, the main “evil” thing Satan is believed to do is simply to lead people away from Christ. Whether this is a good thing or a bad thing depends on how you feel about Christianity.
From a more down-to-Earth point of view, the worst thing Satan is said to do in the New Testament is to drive people insane. (Insanity is blamed on alleged “demon possession.”) Indeed, if one is careless, one can drive oneself insane through exploring the unknown and seeking to “become as gods,” as Satan invites us to do. On the other hand, if one takes reasonable precautions in pursuing one's explorations and ambitions, one can reap great benefits.

Thus, most Satanists do NOT see themselves as "worshiping evil." Rather, most Satanists associate Satan with such values as pride, independence, individuality, knowledge, achievement, thinking for oneself, and exploring unknown and forbidden realms.
Furthermore, contrary to the portrayal of Satanism in horror movies and sensationalistic tabloids, the vast majority of Satanists do NOT see any need to sacrifice animals or commit violent crimes in the name of Satan.
There are many kinds of Satanists.
For most of the past forty years, the most public Satanist spokespeople have been atheistic symbolic Satanists, who do not believe in or worship Satan as a literal entity, but who regard Satan as a symbol of independence, pride, individual ambition, etc. The best-known symbolic Satanist organization is the Church of Satan, founded by Anton LaVey.
There is now a growing movement of theistic Satanists, who do believe in and revere Satan as a deity.
There are many kinds of theistic Satanists. The vast majority do NOT simply accept Christian beliefs except for siding with the Other Guy. The beliefs of most theistic Satanists are based on sources other than just Christianity.

Some theistic Satanists regard Satan as the Christian-era image of a more ancient deity such as the Egyptian god Set, the Greek Titan Prometheus, or the Sumerian god Enki. The Temple of Set is the best-known organization holding such a belief.
Others base their ideas on ancient Ophidian Gnosticism, which venerated the serpent of the Garden of Eden myth. Ophidian Gnostics saw the Biblical God as the Demiurge (an evil god who created the physical world for the purpose of trapping human souls) and the serpent as Sophia, the bringer of wisdom. This theology isn’t popular among today’s Satanists, most of whom have a more favorable opinion of the material world and their own bodies than the ancient Gnostics did.

Some see Satan as “God of this world” in a deistic or pantheistic sense, thereby giving a decidedly non-Christian interpretation to a phrase used in the Bible to refer to Satan (2 Corinthians 4:4).
Many theistic Satanists are polytheistic and regard both Satan and the Christian "God" as just two of the many gods. Some believe that all the gods, including both Satan and the Christian “God,” are really just very advanced extraterrestrial humanoids. Others are polytheistic in a more traditional spiritual sense.

The authors of this pamphlet are founding members of the Church of Azazel, which has a polytheistic theology. We believe that the Christian "God" is not the true cosmic God. To us, the workings of Nature do not suggest that the cosmic creator God desires a personal parental-like relationship with us humans. We believe that the true cosmic God is most likely impersonal, and, therefore, that any god who does relate to humans in a personal way is not the cosmic God. Thus we regard neither the Christian "God" nor Satan as the ultimate God of the universe. We regard Satan as a spirit who rules over the Earth and as a Muse of human innovation.