Short answers, pulled from the story.
The Hebrew word satan was originally a common noun meaning "accuser" or "adversary," derived from a verb meaning "to obstruct or oppose." Throughout the Hebrew Bible it most often refers to human opponents; it began to describe a specific heavenly being in texts such as Job 1-2 and Zechariah 3, where the definite article marks it as a title or office rather than a name.
Origen was probably the first Christian author to use Lucifer as a proper name for the Devil, drawing on the morning star imagery in Isaiah 14:12-15. Saint Jerome later translated the Hebrew hêlêl as Lucifer in the Latin Vulgate, and church fathers including Cyprian and Ambrosius agreed with the identification.
Augustine argued in Civitas Dei that Satan's rebellion was the first and final cause of evil in the world. The fallen angels sinned spontaneously in heaven, without temptation, and so cannot repent; he described them as eternally fixed "in their self-love." Augustine also identified pride, not envy, as the original sin, since pride must logically precede envy.
The Cathars believed the Devil created the entire physical world, a view the former Cathar Sacchoni testified to before the Inquisition in 1250. The Fourth Council of the Lateran in 1215 condemned such dualistic beliefs, formally affirming that God alone created everything from nothing and that the Devil was created good but turned evil by his own free will.
Martin Luther taught that the Devil was real, personal, and powerful, and that evil was an active will against God rather than a mere absence of good. In his Theatrum Diabolorum, Luther listed hosts of greater and lesser devils: greater ones to incite unbelief and heresy, lesser ones to tempt toward greed and fornication, with named figures including Asmodeus from the Book of Tobit.
The Public Religion Research Institute reported in a 2025 survey that 22 percent of Americans agreed or mostly agreed that Satan-worshipping paedophiles control government, media, and financial institutions in the U.S. Scholars Richard Raiswell, Michelle Brock, and David Winter have described this as evidence of a Satanic Renaissance driven largely by American evangelicals and Christian nationalists since the 1960s.