An eye for an eye. A tooth for a tooth. They put one of ours in the hospital, we put one of theirs in the morgue. No matter how you describe it, revenge has been a part of human history since the very beginning. It’s in our very nature to seek retribution on those that we believe to have wronged us.

It’s true – psychologists have long known that revenge seeking is rooted in the reward center of the brain, and exacting vengeance gives us a shot of dopamine just like a runner’s high. With that kind of chemical motivation, it’s no wonder that revenge is ingrained in nearly every culture of the world.

That’s not to say revenge is a good thing, or even healthy. Far from it! Psychologists have also found that while there’s short term gain to be had in revenge, the long term pain far outweighs it. Research shows that exacting vengeance re-opens the emotional wounds from the original wrong, taking much longer to heal. Compound that with the fact the original wrongdoer will now want some revenge of their own, and it can lead to a downward spiral of anger and hate that ends in all-out war.

Lucky for us, revenge is something that is slowly disappearing from the world. But its prevalence throughout history has meant that local cultures have often codified revenge into ritual, and a lot of those rituals are downright scary.

Here are 15 creepy revenge customs that will keep you up at night.

15. Ngayau Headhunting

We begin our tour of revenge with the Dayak people of Borneo, where vengeance often meant one thing: head hunting. Called Ngayau, it was the practice of taking the head of your enemies and then placing them on display. The more heads you have, the more revered and feared a warrior you were.

As with many cultures, having your head hunted by a vengeful relative could be avoided if the culprit was willing to compensate the aggrieved family with adat pati nyawa, or “compensation”. What that compensation could be would depend on the crime: it could be money, food, or even the heads of other people they’ve taken.

To be fair to the Dayaks, the practice is now banned (and for good reason), but headhunting continued as late as the 1960s.

14. The Naga Purge

As I mentioned before, the problem with revenge is how it often leads to a killing after killing until everyone is at war. The Naga people of Northeastern India acknowledged this problem with a unique solution: all grievances between villagers were bottled up, and once or twice a year the entire village would come out in a grand fight where everyone could settle old scores.

If this reminds you of The Purge, you’re not far off.

The curious practice came about from the Naga’s handling of internal strife, where if two men quarreled every member of their village would have to pick a side in the fight. This lead to centuries of civil war, and only with the institution of the bi-annual purging could stability be maintained.

13. Fasil And Diya

Muslim societies have historically been very concerned with familial honor, and the concept of “eye for an eye” is even advocated in the Qur’an. Consequently, the killing of any family member would result in the rest of the male members of that family to seek vengeance against the original perpetrators. This would then cause yet more honor killings, and the cycle of revenge would continue for decades – sometimes even centuries.

Much like the Dayaks, ancient Iraqi leaders noticed this trend of endless violence and developed a way to stop it. Fasil and Diya are negotiated settlements between the feuding families, with Diya enacted for accidental killings and Fasil for intentional ones. The price paid is often a financial one, putting an actual dollar amount on a human life. The American military became well versed in the concept of Diya during the Iraq wars, paying millions to the families of Iraqi civilians killed in the conflict.

12. Consuming The Suangi

The Kombai people of Papua New Guinea are known for a lot of creepy practices, including cannibalism, which features heavily in their belief surrounding the Suangi.

Suangi are evil spirits that are said to consume the internal organs of their victims and then replace them with dirt or grass. The victim then falls mysteriously ill, what with dirt and grass not being particularly healthy in place of your normal internal organs.

On their deathbed, the victim could then name who among the village is actually a Suangi and caused them to become sick. The only way to permanently rid the village of a Suangi is for the victim’s family to kill and eat it. To the Kombai, the only way to cleanse the spirit is through consumption – just don’t forget the Sriracha sauce.

11. Beware the Kurdaitcha

Australian aborigines were just as revenge focused as every other culture. The Arrernte people in central Australia went so far as to make the role of executioner an official position. Called the Kurdaitcha, it was his job to mete out justice.

To the Arrernte, no death was believed to be of natural causes. Every death was the result of evil spirits or spells from some unseen enemy. Sometimes upon their deaths, an Arrernte would speak the name of the person they think caused their death. When that happened the Kurdaitcha would be called to avenge the fallen.

To do it the Kurdaitcha had a number methods, but none were more feared than a mystical bone imbued with spiritual energy. When pointed at the victim it was said to expel that energy, cursing them. They wouldn’t necessarily die right away, but anxiety would eat away at them resulting in a psychosomatic death.

10. Vengeful Spirit or Health Hazard?

We head to the Philippines to meet the Ifugao people for our next ritual. The Ifugao, or “mountain people”, are also very concerned with death, but unlike the Australian aborigines, believe that a natural death is possible. When a loved one dies, their body is garbed in ceremonial robes and then tied to a “death chair” beneath their home and guarded by fires. After 13 days the body is then buried in a mausoleum or coffin.

In cases of untimely or wrongful death, the body is tied to one of the house posts and left to rot. It’s believed that the spirit of the recently departed is then free to seek revenge on whoever killed it in life.

The downside, of course, is now the family of the victim has a rotting corpse tied to their house, which is a bit of a health code violation.

9. Revenge Killings in Egypt

We already know how revenge is seen as a sacred duty in many Arabic cultures, but Upper Egypt takes things even beyond a Game of Thrones level. Blood revenge is a tradition stretching back hundreds of years, with the whole process being codified: if a man is killed, then both the killer and another man in his family must be killed. This would inevitably result in the other family killing 2 of the first, then 4, then 8…

You see where this is going.

The whole process is bound in rules: only men can be targeted, never women or children, and funerals cannot be performed for the dead until they are avenged. This results in decades-long feuds that only come to an end when one side finally says “stop”. And in this case, stop means having both families attend a giant party. So long as nobody else dies, the feud is over.

8. Voodoo Dolls

Many of us think Voodoo Dolls come from the Louisiana and Haiti in the 1700s, where the thousands of African slaves melded their traditions and folklore into a single semi-religious practice. Nothing could be further from the truth.

The act of placing pins into a doll or effigy of someone who’s committed an offense in order to bring about real world pain is actually fairly common in mystical practices around the world, featuring prominently in Asian and Arabic cultures. The practice was then co-opted by a group of British mystics called “cunning folk”, who used the dolls to bring about disease and ill-health on less reputable witches.

The dolls wouldn’t become Voodoo Dolls until the 1930’s when various books and films vilifying African-Americans attributed it to Voodoo practitioners.

7. The Nithing Pole

We owe a lot to Germanic Pagan traditions here in the West, such as Easter and our associating cute fluffy bunnies and eggs with fertility. Most of the more gruesome customs have thankfully died out, but in Iceland, one revenge tradition has stubbornly refused to die.

It’s called the Nithing Pole, or nithstang, and it’s used to curse your enemies. To erect a Nithing Pole, just cut off an animal’s head, wedge the head on the end of a pole, and then implant it into the ground where your enemy can read the ancient runes cursing them.

Unlike many of these revenge rituals, Nithing Poles are still being erected today. In 2006, a farmer erected a Nithing Pole against his neighbor after he ran over his puppy with a tractor, and in 2016 Nithing Poles using cod heads were erected against Icelandic prime minister Sigmundur Davið Gunnlaugsson during economic protests.

6. Maximón And Praying For Vengeance

Although the ancient Mayan gods have largely died out, a few live on in Central American traditions. In Guatemala, the god Maximón is believed to be the continuation of the ancient Mayan deity Mam but blended with Spanish Catholicism. The result is apparently a creepy smoking cowboy wearing aviator glasses.

Guatemalans come to Maximón’s to pray for many reasons, such as good health, success in business, and a peaceful marriage, but also for more sinister purposes. If you’ve been wronged, you may go to Maximón to seek revenge against those who wronged you.

Appealing to Maximón involves prayer as well as sacrifices of cigarettes, money, and liquor, and only after these sacrifices have been made can one ask for his divine assistance.

5. Revenge of the Mulo

When most of us think of gypsy revenge, we think of something along the lines witches and hexes circles made with lambs blood. All of it is just stereotypes, but there is one thing the Romani people have when it comes to revenge: the terrifying Mulo.

Translated literally as “one who is dead”, a Mulo is said to be born when a person is murdered in cold blood. The body then returns to take vengeance on the one that killed it in life.

Which would be fine if the Mulo stopped at just the person that killed it, but they tend to stick around and cause problems for everyone once their vengeance is complete. To prevent a Mulo from rising, ritualistic purification is needed at the time of death which involved placing bits of steel in the mouth, over the eyes, and between the fingers during burial.

4. Appeasing a Yurei

Ancient Japan was another culture very concerned with honor. So concerned, in fact, it was thought that the ghosts of the dead would return to haunt the living until whatever wrongs that had occurred in life had been righted.

These ghosts were called Yurei, and they came in many flavors. An Onryō was a Yurei that returns from purgatory to haunt their living family until justice is served.

Things go from creepy to weird when the family actually tries to seek justice. The family would have to go to court to seek permission to kill the one who murdered the family member. If granted, they can then contract someone to perform the killing, with all of it being state sponsored. Naturally, this meant that justice was reserved for the rich or those who were already proficient in combat.

3. Fair Game

Back when the Church of Scientology was just getting their start in the 1950’s, there were a lot of people who were critical of the budding religion, to the point where they’d often release op-eds condemning the Church. In retaliation, L. Ron Hubbard enacted a policy called Fair Game that targeted groups or individuals that were deemed threats to the Church.

Unlike most entries on this list, Fair Game didn’t result in bloodshed, but it did result in an insidious campaign of harassment where Scientologists infiltrated their targets and left their lives in utter ruin. Personal finances, relationships, and public image were all “fair game” when the Church felt they had been wronged.

The Church of Scientology says the discontinued the practice in the late 60’s, but court cases using the term have happened as late as 2015.

2. Placating the Anirniit

In Inuit tradition, it was believed that everything, both human and animal, had a soul (called an anirniit) and that soul could seek revenge from the afterlife against those that killed it. To appease the soul of the animal that had just been hunted, a ceremony must be performed where ritualistic words for the departed spirit must be spoken, along with a small sacrifice of the animal’s carcass.

Besides having an angry spirit come after you if you fail to perform the ceremony, things could get a lot worse if the Angakkuq (medicine man) ever found out about it. Those that fail to perform the sacred rites are put on latrine duty, and for grievous offenses, the man may be forced to give up his wife until the debt to the village had been paid.

1. Revenge Adult Movies

The most modern practice of revenge involves the internet, nudity, and a jilted lover.

Advances in technology, and especially cameras on cell phones, have made it easy to take photos wherever and whenever you want. During courtship, it’s not uncommon to entice the object of your affection with what would normally be considered scandalous images and sending them via the magic of the internet.

But if things go south in the relationship (like if one party cheats on the other) those photographs can wind up posted online for everyone to see in retaliation. Thus, revenge porn.

The ritual of revenge adult films has become a large enough problem that most countries actually have laws banning the practice, but it doesn’t always stop it from happening. Just ask Kim Kardashian.