I wrote a paper on Satanism recently, here’s e excerpt from it:
As the Christian tradition developed, the notion arose that magicians and diviners performed their amazing feats with some sort of supernatural aid. Since they were obviously not working with God, they, therefore must be working with Satan or demons. This is first suggested by Church fathers such as Origen and later fully developed by Augustine. Aquinas, who would become the official theologian of the Catholic churches, re-affirms this in “Sententiae” where he states that magicians perform miracles through personal contracts with demons. (Lewis 2001, 203) This is the root of the best known legend of Satan; selling one’s soul in exchange for worldly riches and power.
This is exemplified in a legend from the sixth century of the C.E. as told by Rosemary Guiley in Encyclopedia of Witches and Witchcraft (1999). Theophilius was a monk from northern Cicilia. He was modest and when offered a bishop’s position, he declined because he felt he was not up to the job. The man who took the job, however, found strange delight in tormenting Theophilius even bringing charges of sorcery against him. Theophilius, therefore, lost his job. Theophilius wanted revenge and therefore went to see Salatin, an “evil old Jew.” Salatin called up Satan who offered Theophilius revenge in exchange for his soul. Theophilius agreed and signed a pact with Satan in his own blood. Theophilius got his revenge. The man who charged him was thrown out of office and Theophilius was installed in his stead. But Theophilius was not happy. He worried about his fate of eternity in torment. He began to pray to the Virgin Mary and God for his salvation. God forgave Theophilius, much to his delight. Theophilius made a public confession and burned the pact. He lived the rest of his life piously and in peace (Guiley 1999, 329).
Lewis (2001, 88) and Guiley (1999, 122) both note that this legend is the basis for the various stories about Faust. The legend of Faust is based upon a real person, Dr. George Faustus, a German who lived circa 1480 to 1539 (or 1540). What is fact and what is fiction in his life is unclear. It is believed he was one of the charlatan magicians who, during the Renaissance, traveled around Europe, entertaining at fairs and royal courts. Stories circulated that he had sold his soul for his amazing magical powers. These stories contained many of the pact-with-the-devil elements that were popular during the Renaissance: youth, the seduction of young women and fine food and wines. According to one story, when the contract was up, the Devil came to collect Faust’s soul. The story goes, after midnight one night a terrible wind wailed around Faust’s house. Neighbors could hear his cries for help, but no one went to aide him. The next day, they found his twisted body outside in a pile of dung. In his house, his blood, brains and teeth were splattered across the walls (Guiley 1999, 123).
References:
Lewis, James R. “Satanism Today: An Encyclopedia of Religion, Folklore and Popular Culture” 2001.
Guiley, Rosemary Ellen “Encyclopedia of Witches and Witchcraft 2nd Ed.” 1999.