Luciferianists were theistic Satanists who celebrated the spirit-being Lucifer. Some adherents identified the figure with the biblical character Satan, while others associated him with old-world mythologies and occult lore.

The 12 century document, The Gesta Treverorum, or "Deeds of Treven," are the records of the Archbishops of Trier and the writings of Popes, amassed by monks from St. Matthews Abbey located in Trier, France. The documents speak of the existence and activity of Luciferians. Pope Gregory IX (1145-1241) writes that Luciferians argued that Lucifer was unfairly expelled from heaven.

Many groups today claim an affiliation with historical Luciferianism, including The Order of the Phosphorus, The Ordo Luciferis, The Ordo Luciferi, The Temple of the Dark Sun, and The Neo-Luciferian Church.

Sources>Catholic Encyclopedia