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Serial killers. Throughout history we have been haunted by such madmen and women, and we probably will be forever more. However, what makes a serial killer or killers even scarier is when their dark and bloody stories are steeped in the world of the occult and the supernatural, and there have been many of these human monsters who have sought to consort with magical forces and monsters of a less human kind. - Brent Swancer (mysteriousuniverse.org)

A short list to give you an idea:

• Jeffrey Dahmer thought that building an altar from his victims’ preserved skulls and bones would give him a supernatural edge, socially and financially. He killed 17, but this provided no immunity from conviction or from the fellow inmate who killed him. 
•  According to accomplice confessions, Robin Gecht inspired a group of young men in Chicago to murder women, remove their breasts, and use the flesh in an occult ritual.
•  In Singapore, self-styled medium Adrian Lim sacrificed the children he had raped to the goddess Kali. 
•  “Night Stalker” Richard Ramirez left satanic pentagrams on some victims and forced others to swear allegiance to Satan. When arrested, he claimed to be a "minion" of the Dark One. 
•  In Oklahoma City, Sean Sellers murdered a convenience store clerk as “practice” before killing his mother and stepfather. His schoolmates had voted him as the person most likely to become a vampire, because he carried the Satanic Bible. “Demons were the beings that would do things I wanted done,” he wrote in his confession. “They were the keys to the power Satanism promised.”
•  Adolfo de Jesus Constanzo and Sara Maria Aldrete sacrificed an unknown number of people in Motamoros, Mexico, to magically thwart police investigations during their drug deals. The decapitated and mutilated bodies of 15 men and boys turned up in a mass grave.
•  Of course, there are many accounts that identify Jack the Ripper as a man with supernatural connections – especially since he was never caught. During an era of flourishing secret societies, this is no surprise.- (https://mysteriousuniverse.org/2017/11/occult-serial-killers-and-the-supernatural/)
• Leonarda Cianciulli visited a fortune teller and was given the grave news that all of her children were going to die before she did. Leonarda became somehow convinced that the only way to save them was to perform blood sacrifices to appease whatever dark forces were circling her and her family. She axed a client Faustina Setti in a blood sacrafice and made soap and candles with the body. She then murdered Francesca Soavi by drugging her and dismembering her once again making soap and candles with her body parts. (summary various sources)
• Rodney Joey Blach, the Freemont Bomber. Rodney Joey Blach had a highly intelligent criminal mind. He was a gifted chemist with an extensive background in law enforcement AND astrology. He had worked for the Chicago Police Department from 1975-1979 as a microanalyst. He had testified many times in court as an analyst for fingerprints, soil and blood. He knew the “system” extremely well. When his locker was eventually searched numerous bomb-making materials, various books on how to build bombs and explode bombs were found. Also found were hundreds of personally written notes and pages relating to astrology. - https://www.lightforcenetwork.com/logos-overseer/witness-prosecution-%E2%80%93-real-astrology-work
• David Berkowtz, the Son of Sam Killer. A bit of a debunk about David - David was not part of a demonic cult. It is true that he became obsessed with the occult and worshipped Satan prior to his murders, but he acted alone throughout his killing spree. Although he hated the nightly barking of Harvey the dog, it did not order him to murder anyone. Instead, David explained to me that he felt like "a soldier on a mission" when he went out to kill. - Dr. Scott Bonn (Interview with Berkowitz, https://www.cbsnews.com/news/serial-killer-david-berkowitz-aka-son-of-sam-tells-professor-i-was-once-an-evil-person-in-prison-conversation/)
• In Canada, a 7 year old boy is murdered and partially eaten by a 14-year old. Elyse Pahler, a fifteen-year-old California girl who snuck out of her parents’ home to meet three male acquaintances from school. The boys (teenagers who had a heavy metal band) killed Elyse as a sacrifice to Lucifer so their band would take off. In Northport, New York, 17-year-old Ricky Kasso murders his friend, 17-year-old Gary Lauwers, deep inside Aztakea Woods over ten stolen bags of angel dust. He later tells police that Satan appeared to him in the form of a crow to tell him he was pleased with the deed. - https://en.wikipedia.org/wiki/Killer_Kids
• Leroy Carter Jr. was sleeping in the bushes of Golden Gate Park when he was attacked and decapitated. The San Francisco Police brought in an officer who specialized in the occult. According to her, the murder was likely part of a dark ritual involving Palo Mayombe, a black magic offshoot of the Afro-Caribbean religion Santeria. The ritual made a brew from the victim’s brains and perhaps the ears and the nose. She predicted that the head would be returned after 42 days, once the ritual was complete. It was. - https://listverse.com/2014/11/29/10-unsolved-murders-with-strange-links-to-the-occult/
• On December 16, 1979, the bodies of 53-year-old Howard Green and 33-year-old Carol Marron were found on the shoulder of Route 80 in West Patterson, New Jersey. Both had been beaten on the left side of their face and then stabbed in the right eye. In each of the victims’ hands lay a clump of hair. Their bodies had been completely drained of blood, most likely with a veterinarian’s syringe. The police searched the couple’s Brooklyn apartment and found occult paraphernalia. Journalist Murray Terry received a letter from an anonymous friend of Carol Marron, who said that Green had been looking into Ordo Templi Orientis, a religion started by famed occultist Aleister Crowley. The detective on the case was sure that the murders were occult in nature and that more than one person had committed them. https://listverse.com/2014/11/29/10-unsolved-murders-with-strange-links-to-the-occult/
• Patrick Erjabor (identified victim) - On September 21, 2001, the torso of a young boy floated in the Thames River near the Tower Bridge. It had been in the water for about 10 days before it was found. London Police called the boy “Adam.” A medical examination of the torso showed that the body had been dissected as though by a professional butcher of animals. The skin had been cut, and then a single chop had severed each limb. It was theorized that Adam was part of a human sacrifice to one of the 400 gods of the Nigerian Yoruba people. A year later, suspicion fell on a human smuggler named Kingsley Ojo. The police searched Ojo’s apartment in 2002 and found a bag with a mixture of bones, sand, and gold flecks—a mixture also found in Adam’s stomach. The apartment contained a videotape labeled “rituals,” showing the ritual dismemberment of a human victim. Besides those clues, police couldn’t find a connection between Adam and Ojo. Ojo was sentenced to four and a half years in prison for human smuggling before being deported to Nigeria. The person or persons behind the ritual dismemberment of the young boy are still unknown. It was believed that he died to bring about “good luck.” http://https://listverse.com/2014/11/29/10-unsolved-murders-with-strange-links-to-the-occult/