Known as the “Vampire of Dusseldorf” and the “Dusseldorf Monster,” Peter Kurten murdered at least nine people in 1929 in Dusseldorf, Germany. He’s believed to have attempted upwards of 31 murders throughout his lifetime, though, and honestly, the whole case is so weird, you can’t make it up. What made him so difficult to catch is that he kept changing up his MO — sometimes he’d use a knife; other times, a sharpened pair of scissors; and still others, a hammer. For some time, police weren’t even sure the same person was behind all of the crimes.

He was eventually caught due to — of all things — a mail mistake. 20-year-old Maria Budlick escaped Kurten’s attempt to strangle and assault her in the Grafenburg Woods on May 14, 1930. She didn’t report the assault to the police, but she wrote about it in a letter to a friend — a letter which she addressed incorrectly. Because of the incorrect address, a clerk at the post office opened it, read it, and forwarded it to the police, who then interviewed Budlick. She said that the reason Kurten had let her go was that she told him she could not remember his address, where he had taken her before taking her to the woods… but she remembered it just fine. What's more, she was able to lead the police there.

It all unraveled from there.

Kurten was arrested, tried, and found guilty of nine murders and seven attempted murders. He was executed by guillotine on July 2, 1931. His head was subsequently dissected and mummified; these days, it’s displayed as an exhibit at the Ripley’s Believe It or Not! In Wisconsin Dells, Wis.

A caveat concerning the “you’ve probably never heard of” bit for this one: You’ve probably never heard of Robert “Willy” Pickton if you’re not from Canada. If you are from Canada, though, you’re probably quite familiar with him. Between 1983 and 2002, Pickton, a pig farmer from Port Coquitlam, British Columbia, killed at least six women who had all gone missing after visiting the farm — although he was charged with the murders of 20 more. The women were typically in their 20s, although some were older; additionally, many of them were indigenous.

He was caught after police obtained a warrant to search the farm for illegal fireworks on Feb. 6, 2002, but a second court order sealed the deal: This order enabled the police to search the farm for the BC Missing Women Investigation, during which time they discovered personal items belonging to the missing women. On Dec. 9, 2007, Pickton was found guilty of six counts of second-degree murder and sentenced to life in prison with no chance of parole for 25 years.

I’m not sure I’d call this a silver lining, but there is at least one important thing to have come out of the Pickton case: As The Independent pointed out in 2013, “the case continues to shed light on Canada’s most shameful secret: how its most ignored underclass — indigenous women — is preyed up by men with impunity, and with terrifying consequences.” According to The Independent, 67 women went missing during the time that Pickton was active, nearly two-thirds of whom were aboriginal; what’s more, the Native Women’s Association of Canada told The Independent that 582 cases of indigenous women being murdered had been documented as of March 2010, 39 percent of which had occurred just between 2000 and 2010. These cases are not often investigated by authorities, and that is a huge, huge problem.

Amelia Dyer is believed to be one of the most prolific serial killers in history: Over the course of about two decades the late 1800s in England, she is thought to have killed several hundred babies and small children. Only 12 have been confirmed — but “only 12” is, I feel, still a horrifying number.

A widowed nurse, Dyer was what was known as a “baby farmer” — someone who took in unwanted babies and children for money. She had two children of her own, and did initially actually take care of her charges; however, she eventually began letting the children die of neglect. After completing six months in prison for the charge of infant neglect, she took it a step further and began killing the children who came into her "care" immediately after receiving payment.

The remains of a baby girl were discovered from the Thames at Reading in March of 1896 and traced back to Dyer. A trap was laid for her by the police, with a decoy “new client” leading to a raid on Dyer’s home. She was arrested on April 4 and charged with murder; after a guilty verdict was returned, she was hanged at Newgate on June 10, 1896.

You’ve probably heard the phrase “lonely hearts killers” — murderers who lure their victims in via the personal ads in newspapers — right? Although we may think of these kinds of killers as fairly modern, they’ve been around for much, much longer than that. Bela Kiss, for example, spent many of the early years of the 1900s corresponding with women he connected with through ads he placed in the newspaper, although they never seemed to stick around for long. In 1914, Kiss was conscripted and went off to fight in the First World War, leaving behind both his home and a collection of large, metal drums on the property. He had told his neighbors at the start of the war that he was using them to store gasoline in preparation for rationing.

During the summer of 1916, Kiss was still away — but police in Budapest received an unsettling phone call about him nonetheless: When soldiers in need had approached the constable of Cinkota, where Kiss had lived, the constable remembered Kiss’ metal drums and their supply of gasoline. However, when one of the drums was opened, there was no gasoline found within it. Instead, there was the body of a woman.

The other drums contained more bodies, too. By the time a full search of Kiss’ property had concluded, 24 bodies had been found.

Kiss, however, never was. Attempts to locate him were fruitless; the closest authorities came was in October of 1916, when a letter led them to a Serbian hospital in which Kiss had allegedly been recuperating. By the time they arrived, though, he was already gone, having placed the body of a dead solider in his bed instead.

We still don’t know where he went.

Known as the Chessboard Killer, Alexander Pichushkin was convicted in 2007 of killing 48 (48!) people in Moscow. He preyed primarily on elderly and homeless people, often inviting them to share a drink with him over his supposedly dead dog’s grave in Bittsevsky Park; then, after the victims were drunk, he would beat them with blunt instruments. He was caught after he killed a woman he worked with at a grocery store — she had left a note for her son saying that she was going for a walk with Pichushkin right before her death. He was charged with 48 counts of murder and three of attempted murder before being convicted of all 51 counts. He’s now serving life in prison.

As for the name “the Chessboard Killer”? That came from one of the details that emerged after Pichushikin’s arrest: Police found a chessboard he had kept, with dates written on more than 60 of the 64 squares — dates which corresponded with the murders he had committed.

Born in Charlestown, Mass. on Nov. 29, 1859, Jesse Pomeroy has the dubious "honor" of being the youngest person ever to be convicted of first-degree murder in Massachusetts history. His rap sheet reads like Lord Voldemort: The Early Years — except worse, because it is absolutely, 100 percent true.

It’s believed that Pomeroy was responsible for a series of attacks against young boys between 1871 and 1872, in which the boys were drawn to secluded areas and beaten and knifed by an older boy; Pomeroy was later arrested, charged, and found guilty of the attacks, landing him in the State Reform School for Boys at Westborough at the age of 13.

In February of 1874, he was paroled… and in March of 1874, a 10-year-old girl was reported missing, while in April of 1874, the body of a four-year-old boy was discovered at Dorchester Bay. Pomeroy was arrested after the discovery of the four-year-old; the 10-year-old’s remains were later found in the basement of his mother’s dressmaking shop.

He was found guilty of the murder of the four-year-old on Dec. 10, 1874; later, he would also be found guilty of the murder of the 10-year-old, although he’s believed to be responsible for seven more murders in addition to those two. He was sentenced to death. However, his sentence was later commuted to life in prison; he spent most of his time in the Massachusetts State Prison in Charlestown. In 1929 at the age of 70, Pomeroywas transferred to Bridgewater Hospital, where he died three years later.

Randy Steven Kraft is often referred to as the Scorecard Killer — a name which refers to the list of coded phrases found in his car which is believed to have been a sort of system for keeping track of the murders of boys and men he committed primarily in California between 1972 and 1983. In May of 1989, Kraft was found guilty of 16 counts of murder, one count of sodomy, and one count of emasculation, although he’s believed to have murdered as many as 51 additional men and boys. Twenty-two of his suspected 67 victims remain missing and unidentified.

Kraft’s first victim is suspected to be Wayne Joseph, Dukette, who was last seen at his place of employment (Dukette was a bartender), the Stables Bar in Sunset Beach. His body was discovered at the bottom of a ravine in Orange County on Oct. 5, 1971; his car, however, remained in the parking lot at Stables. The first entry on the “scorecard” reads “Stable.”

As so often seems to be the case, Kraft was eventually caught for an unrelated reason: On May 14, 1983, he was pulled over and arrested for drunk driving. In the passenger seat of his car was the body of a young man — 25-year-old Terry Lee Gambrel.

Kraft was sentenced to death on Nov. 29, 1989 — a sentence which was upheld by the California Supreme Court on Aug. 11, 2000 — and currently remains on death row at the San Quentin State Prison. Despite his conviction, he continues to deny his guilt.

The Carsons only just fit the widely accepted definition of “serial killers” in the United States; according to the FBI, “the term ‘serial killings’ means a series of three or more killings, not less than one of which was committed within the United States, having common characteristics such as to suggest the reasonable possibility that the crimes were committed by the same actor or actors.” Michael Bear Carson and Suzan Carson, who were involved with the counterculture in Northern California during the late ‘70s and early ‘80s, have been convicted of three counts of murder, with each of the crimes having been committed between 1982 and 1983.

Their victims were Keryn Barnes, a 22-year-old aspiring actress who had shared an apartment with the Carsons in Haight-Ashbury; Clark Stephens, who worked on a marijuana farm with the Carsons in Aldepoint, Calif.; and Jon Charles Hellyar, who picked the Carsons up as hitchhikers near Bakersfield. Stephens and Hellyar were both shot, while Barnes was beaten witha blunt object and stabbed.

Michael Bear Carson shot Hellyar after an altercation at the side of the road, so there were quite a few witnesses; one of them called the police, and although the Carsons attempted to make a getaway in Hellyar’s car, they were caught and arrested after a high-speed chase. After the guilty verdict came down relating to Barnes’ murder, they were sentenced to 25 years in prison; the later convictions for the murders of Stephens and Hellyar resulted in sentences of 50 years to life and 75 years to life. The convictions were upheld by a state appeals court in 1989.

According to Michael’s daughter, Jenn, who spoke with the Arizona Republic in 2010, the Carsons believed they were destroying “witches” whom they had deemed to be evil.

Although Herman Webster Mudgett, better known as H. H. Holmes, is often called America’s first serial killer, that’s not strictly accurate. Long before Holmes build his “Murder Castle” during the 1893 Chicago World’s Fair, the Harpe Brothers — Micajah “Big” Harpe and Wiley “Little” Harpe, sometimes also cited as Harp — were wreaking havoc in Tennessee, Kentucky, Illinois, and Mississippi in the years following the Revolutionary War (during which, interestingly, they sided with the British).

Originally from North Carolina, the Harpes spent their lives roaming around the United States, always leaving destruction in their wake. They set fire to buildings, they stole, they assaulted women, they attacked men — and they killed a horrific number of people. We know they committed at least 39 murders, although it’s possible that they may have been responsible for the deaths of upwards of 50 people.

Eventually, they joined up with the Mason Gang, a gang of river pirates led by Samuel Mason — which turned out to be the cause of their downfall: The Harpes and another pirate, James May, killed Mason, intending to collect the hefty reward that was being offered for his head; however, when they went to trade in the head for the cash, the outlaws were recognized and arrested. Although they initially managed to escape, they were later recaptured and executed in January of 1804.

The most disturbing thing about the Harpes? The fact that they weren't primarily motivated by money or other financial gains. They killed for fun.