Despite the claims of some illiterate devil worshipers, Anton LaVey was an atheist. Meaning, he did not believe deities to exist. That includes Satan as an actual deity. There are multiple, independent sources where he states this position. You can read many of these in the article “What, The Devil?” at https://www.churchofsatan.com/what-the-devil/ .
Here is an additional quote, from 1971, from his “Letters from the Devil” column: “The Satanist fully recognizes that Satan is nothing more than a symbolic entity representing man himself; his carnal and physical desires, his freedom from enshackling doctrines, and his intellectual capacity to reject those elements of man-made law which prevent him from engaging in life to the fullest. To suppose that Satan is a substitute for the Christian “God” is entirely erroneous. Man himself is the God; Satan is merely the symbolic representation of the WHOLE man and is given a place in Satanic ritual as a strengthening device to affirm one’s own convictions.”
The topic of atheism and non-theistic religions is also thoroughly covered in Satansplain #016:
In 1973, a double-record set called “The Occult Explosion” included an interview clip of LaVey, explaining Satanism. He explicitly states at the start, “Satan is to us a symbol, rather than an anthropomorphic being.” Some devil worshipers try quote-mining the next parts where he explains that any members of the Church of Satan “who are mystically inclined, would prefer to think of Satan in a very real, anthropomorphic way. Of course, we do not discourage this because we realize that to many individuals, a picture — a well-wrought picture of their mentor, or their tutilary divinity, is very important for them to conceptualize, ritualistically. However, Satan, symbolically, is a teacher: the informer of the whys and wherefores of the world.” He then goes on to explicitly state that Satanists are not Satan worshipers. In any case, using anthropomorphic images of Satan for ritualistic purposes and to help conceptualize concepts still isn’t “theistic Satanism”, and LaVey stresses that Satan is only a symbol.
Another tiresome claim is that LaVey claimed to believe in Satan in a 1974 Cloven Hoof newsletter. The letter in question was written by Michael Aquino, whose conflicting theistic beliefs led him to his exit from the Church of Satan. Anteater-worshiping Aquino of course spent the rest of his life trying to discredit LaVey and the Church of Satan. Read LaVey’s words from his essay Hoisted by His Own Patois.
Yet another lame argument is that Magistra Blanche Barton “confirmed” LaVey’s belief in a literal Satan in “The Barton Letter”. But rather than answering the question “Did Anton LaVey believe in Satan?”, she chose to answer a different question: “Did Anton LaVey believe in Satanism and the Church of Satan?” He certainly did.
Additionally, keep in mind that an atheist who personally eschews the term “atheist” for themselves is still an atheist. George Carlin for example didn’t like using the term for himself, even though he undoubtedly was an atheist. The same with Tom Lehrer, Bill Gates, and many other famous atheists. A lot more people who don’t believe in a deity, however, became more comfortable with using the term by the 2000s with the New Atheist movement. The fact that the Church of Satan has likewise become more open with using the term still doesn’t change the fact that we’ve always rejected the notion of gods, thus making us atheists by definition.
Another common argument we hear is, “You can’t be an atheist if you say you are your own god. Because that means you believe in a god and are thus not an atheist!” This argument stupidly overlooks the fact that saying “I am my own god” is symbolic. When a Satanist says, “I am my own god”, it does not mean, “I believe myself to literally be a supernatural deity.” Rather it means, “I put my own self in the role that most other people put ‘God’ in. Meaning, I am the one whom is most important in my life. I am the one I ultimately aim to please. I am the one most responsible for my life, for better or worse. If I run into problems in life, it is ultimately up to myself, not an actual deity, to find a way out of those problems.” An analogy I use is that it’s similar to how an entrepreneur can simultaneously say, “I don’t have a boss” and “I am my own boss”; only an illiterate would call this hypocrisy.
In summary, people claiming to be “Theistic LaVeyan Satanists” seemingly can’t read, or at least lack the mental capacity to comprehend metaphors. Anybody claiming that Anton LaVey “really” believed in a literal Satan and that the Church of Satan’s position somehow changed later, is simply lying. Don’t take my word for it; look at the documented evidence instead of going by hearsay, anecdotes, or by poetic waxing misread by people who can barely type.