Saint Cyprian of Antioch
Strange but true: Until 2001, and for at least 700 years before that, St. Cyprian of Antioch was officially the patron saint of witches, magicians and sorcerers.
Cyprian was a pagan sorcerer who was reputedly able to summon and control demons. His magic, however, was foiled by the unassailable Christian faith of Justine, a woman he desired.
Cyprian converted to Christianity, became Bishop of Antioch while Justine became the abbess of a convent. The two were later martyred together by the Roman Emperor, Diocletian.
They were recognized saints at least as early as the 13th century. That’s when their shared feast day first appears in the calendar of Roman Rites.
Cyprian and Justine were removed from the official list of saints (The Roman Martyrology) in 2001, but an important part of Cyprian remains. It is Cyprian of Antioch—the man who summoned demons in his pagan youth—who wrote the rites of exorcism still used by the Church today.
Bonus Trivia: In Scandinavian folk magic, “Cyprianus” is the common name for any manuscript collection of spells, and has a dark connotation to it.