A Christian movement believed the Old testament God was in fact Satan

Catharism from the Greek: καθαροί, katharoi, “the pure (ones)”) was a Christian dualist movement that thrived in some areas of Southern Europe, particularly northern Italy and southern France, between the 12th and 14th centuries. Cathar beliefs varied between communities because Catharism was initially taught by ascetic priests who had set few guidelines. The Cathars were a direct challenge to the Catholic Church, which denounced its practices and dismissed it outright as the Church of Satan.

Catharism had its roots in the Paulician movement in Armenia and the Bogomils of Bulgaria, which took influences from the Paulicians. Though the term “Cathar” has been used for centuries to identify the movement, whether the movement identified itself with this name is debatable. In Cathar texts, the terms “Good Men” (Bons Hommes) or “Good Christians” are the common terms of self-identification. The idea of two Gods or principles, one being good the other evil, was central to Cathar beliefs. The good God was the God of the New Testament and the creator of the spiritual realm, as opposed to the

Christian bad God, whom many Cathars identified as Satan, creator of the physical world of the Old Testament. All visible matter, including the human body, was created by Satan; it was therefore tainted with sin. This was the antithesis to the monotheistic Catholic Church, whose fundamental principle was that there was only one God who created all things visible and invisible. Cathars thought human spirits were the genderless spirits of Angels trapped within the physical creation of Satan, cursed to be reincarnated until the Cathar faithful achieved salvation through a ritual called the Consolamentum. From the beginning of his reign, Pope Innocent III attempted to use diplomacy to end Catharism, but in the year 1208 Innocent’s papal legate Pierre de Castelnau was murdered while returning to Rome after preaching the Catholic faith in southern France. With the option of sending Catholic missionaries and jurists extinguished, Pope Innocent III declared Pierre of Castelnau a martyr and launched the Albigensian Crusade