J.K. Rowling's Harry Potter stories are filled with magical creatures, and not all of them are friendly. In fact, some of them are so evil and frightening that even the most powerful witches and wizards steer clear of them.

In Rowling's Wizarding World, few creatures inspire dread and fear like the Dementors. As otherworldly creatures who feed on feelings of hope and happiness, Dementors drift through the air in tattered black rags that barely conceal their lifeless grey skin.

Anyone unfortunate enough to be caught in their vicinity feels a chill in the air as all light and hope is snuffed out around them. The mere presence of such a creature can be extremely hazardous to a person's health, but the Dementor's Kiss is considered to be a fate worse than death: the monstrous being sucks out their victim's soul and all that remains is an empty shell.

Despite the dark power they wield, the Ministry Of Magic made use of them for centuries, primarily as guards to the nightmarish prison of Azkaban. Predictably, the dark creatures defected to Voldemort's cause when the dark wizard made his return.

To shed some light on these dark creatures, here are the 15 Things You Didn't Know About Dementors in Harry Potter.

They're Blind, But Can Track Emotions

Dementors in Hogwarts Castle

Dementors have no eyes, so they can't see like humans or other creatures. You might think their blindness would make them easy to avoid, but unfortunately their other senses make up for it.

Their primary means of locating and hunting down prey is their ability to detect emotions. One example of this was their invasion of a Quidditch game at Hogwarts during Harry's third year at the school. Already patrolling the school grounds for signs of Azkaban escapee Sirius Black, the Dementors were drawn to the intense emotions emanating from the Quidditch pitch, both from the players and the fans assembled to watch the game.

In Azkaban, they are able to use this ability to track the locations of their many prisoners, making them ideal guards.

They Can't Be Killed, But They Can Die Off

Dementors at Azkaban in Harry Potter

Dementors aren't alive in the traditional sense, which unfortunately means that they can't really be killed, either.

There are ways to defend oneself against them, of course-- most notably the Patronus Charm. A positive force powered by the goodwill of the wizard can repel and chase off the creatures. The only problem is that goodwill can be hard to come by in the presence of Dementors, so even the most powerful witch or wizard can struggle to produce their Patronus when they need it most.

A Patronus can't kill a Dementor, though, and neither can the killing curse. The only thing that can kill a Dementor (or make them fade away, at least) is to starve them of the emotions they feed on. A better world, like the one (presumably) created after Voldemort's death, would be anathema to them, so it's likely that their numbers dwindled after the Dark Lord's demise.

J.K. Rowling's Pre-Potter Depression Inspired Them

JK Rowling

J.K. Rowling has been open about the difficulties she faced before becoming the most famous author in the world. As a single mother trying to support her family and launch her career, she struggled with depression, and it was those feelings of despair that inspired her when she created the Dementors.

In a 2000 interview with The Times, she explained how her depression would eventually become the key to understanding the feeling of dread the Dementors leave in their wake, describing it as: "... (the) absence of being able to envisage that you will ever be cheerful again. The absence of hope. That very deadened feeling, which is so very different from feeling sad."

By using her remarkable creativity, Rowling was able to tap into one of the most painful experiences of her life and use it to add depth to her fantastical stories.

They Were First Discovered on Azkaban Island

Harry Potter Azkaban Prison

Though their true origins remain a mystery, Dementors were first discovered on the island that would one day become the wizard prison known as Azkaban. The island in the North Sea was home to a dark wizard named Ekrizdis, who was so cruel (and crazy) that he lured Muggles to his shores in order to torture and kill them. After the dark wizard died, the previously hidden island was revealed to the wizarding world, prompting the Ministry of Magic to investigate.

Those charged with investigating the island and its fortress found untold horrors, but none were greater than the Dementors themselves. It's unclear whether Ekrizdis himself created the creatures, or if they were simply attracted to the pain and suffering that emanated from the island. What was clear was that the nightmarish things had no interest in departing, so the Ministry left the island untouched.

Azkaban Prison Was Created To Make Use Of Them

In 1718, Minister For Magic Damocles Rowle decided that the island of Azkaban would be an ideal place to house the dregs of the wizarding world. The abandoned fortress became a jail for dark wizards, and the Dementors were enlisted as guards. Though the creatures aren't loyal by nature, they readily accepted their new responsibility, as they would once again have a bevy of emotions to feed on.

Azkaban served its intended purpose for hundreds of years, due in large part to the presence of the Dementors. Prisoners there tended to go insane (if they weren't already), and some in the wizard community complained about the inhumanity of leaving them at the mercy of the creatures.

However, the Ministry had no better use for them, and there was concern that depriving them of their food source could lead to greater trouble, so the prison and its guards remained intact.

They Appear In Dark, Decayed Places

A dementor attacks Dudley Dursley in a scene from Harry Potter and the Order of the Phoenix

Nobody has had the opportunity (or the desire) to study the Dementors at length, but it's generally accepted that they don't breed like most creatures. Instead, they grow in (or at least are drawn to) dark, dank places.

It's unclear whether the environment and its negative energy creates them, but it seems likely. There are clearly no infant Dementors, so they presumably arrive fully formed and ready to feed off those around them.

Just as Muggles might avoid dark alleys and filthy hovels for fear of muggers (or worse), wizards avoid such places because they're the perfect home for Dementors. Any location that is infested with decay and depression will draw them in, which is why so many of them were found on Azkaban island.

Had Voldemort succeeded in conquering the wizarding world, there's no telling how prevalent the Dementors would have become.

Chocolate Lessens Their Effects

Chocolate Frog Card From Harry Potter

Who doesn't love chocolate? Dementors probably aren't fond of it, as the creamy goodness of chocolate serves as an unlikely medicine for those who encounter the creatures.

After Harry's encounter with a Dementor on the Hogwarts Express, Professor Lupin gives him chocolate, and it brings the young wizard out of his funk. There are no magical properties to the treat-- Muggles have enjoyed it for centuries, after all. It simply tastes great and improves one's mood, which is exactly what's needed after a Dementor attack.

However, all the chocolate in the world won't cure a witch or wizard of the Dementor's negative effects. The only permanent solution is driving them off with a Patronus and counteracting the depression they leave behind.

They Create A Mist Visible To Muggles

Dementor on Hogwarts Express in Harry Potter

It's well established that Muggles (and even Squibs) can't see magical creatures or phenomena. They can, however, feel the effects of a particularly powerful spell or creature. If a Muggle is having a good day and suddenly feels a chill and a series of negative emotions, it's entirely possible that they've just unknowingly passed by a Dementor.

When the Dementors betrayed the Ministry and joined Voldemort's cause, this effect was heightened. In 1996 (as depicted in The Half-Blood Prince), there were so many Dementors that they created a mist in the summer (visible to both Muggle and wizard communities).

The presence of dementors also resulted in a growing public dissatisfaction that manifested itself in a number of ways, including failing confidence in the British Prime Minister.

Prolonged Exposure Leads To Depression and Insanity

Death Eaters Bellatrix in Azkaban

Prison is a pretty depressing place to be in the human world, so just imagine how bad it is for wizards. Azkaban's reputation as a horrific place is well earned. Its remote location in the middle of the North Sea makes it essentially impossible to escape from, and the isolation is no treat either. However, the guards are the real menace.

Prolonged exposure to Dementors will send even the strongest mind into a pit of madness, so just imagine what happens to witches and wizards who are kept in close quarters with the creatures for years on end. It's safe to say that, if a wizard isn't insane when he's sent to Azkaban, he is by the time he leaves (if he ever does).

Look at Bellatrix Lestrange, for example, who was stark raving mad. She may have never been the picture of mental health, but her time in Azkaban eradicated whatever was left of her sanity.

They're Less Effective Against Animagi

Sirius Black Animagi in Harry Potter

Not every witch and wizard is capable of becoming an Animagus. The ability to assume the form of a beast is a difficult one to master, but those who do are able to gain an indispensable advantage.

Sirius Black, James Potter, and Peter Pettigrew learned to use the complicated spell as students at Hogwarts so that they could keep their friend Remus Lupin company on the nights he transformed into a werewolf.

Later in life, those skills would come in handy for both Peter and Sirius, though they would use them to different ends. Peter escaped judgement by becoming the rat Scabbers, while Sirius was sent to Azkaban for a crime he didn't commit. While there, his ability to transform into a dog served him well, as it confused the Dementors and compromised their ability to feed off of him.

Dark Wizards Aren't As Susceptible To Them

Voldemort with the Elder Wand

Dark wizards do feel the effects of Dementors-- if they didn't, Azkaban wouldn't be a very good prison. However, their villainous natures make them less susceptible to the damage the creatures can do.

After all, Dementors feast on positive emotions, and dark wizards don't spend a lot of time cultivating those. Wizards like Voldemort and his Death Eaters are consumed with anger, jealousy, fear, and hatred, and those emotions don't make satisfying meals for Azkaban's guardians. They much prefer the happy, fond memories from more positive people.

This is probably why the Dementors joined Voldemort's forces during the Second Wizarding War, as a world ruled by him would have undoubtedly been a pretty depressing place for a lot of good people (in other words, the perfect Dementor feeding ground).

A Species Of Wasp Is Named After Them

The Ampulex Dementor Wasp

There are Harry Potter fans in all walks of life, which explains how the Dementor became the namesake for a particularly nasty species of wasp.

Classified in 2014 at the Museum für Naturkunde in Berlin, the Ampulex dementor is a wasp that has a unique way of hunting the cockroaches that provide food for its larvae. The sting of the dementor wasp releases a toxin into the cockroach that renders them unable to control themselves. The result makes them easy prey, and leaves them in something of a fugue state-- almost like they've had their soul sucked out by a Dementor.

Visitors to the German museum were able to choose from four possible names for the species, and the imaginative Harry Potter tribute was declared the winner. The dementor wasp can be found in Thailand.

Sirius Black Learned How To Repel Them

Sirius Black sits in an Azkaban cell in Harry Potter and the Prisoner of Azkaban

Sirius Black had a difficult (and tragically short) life. He lost his best friends to Voldemort and was imprisoned in Azkaban for a crime actually committed by his traitorous former friend Peter Pettigrew.

Though he possessed remarkably strong character, his mind was understandably addled when he finally escaped from the prison. Still, the damage wasn't nearly as bad as it could have been.

Sirius was able to fend off the Dementors by taking a unique approach to his imprisonment. Unlike other prisoners, Sirius didn't cling on to his happy memories of better days, which would have invited the attention of the creatures.

Instead, he nursed his obsessions: his hatred for Voldemort and Peter Pettigrew, his frustration at the injustice of his situation, and his concern for his godson Harry's safety. These thoughts and emotions weren't very satisfying for the Dementors, so Sirius was spared the worst of their effects.

They Were Banished After The Second Wizarding War

The Battle of Hogwarts in Harry Potter and the Deathly Hallows Part 2

We don't know much about what happens to the wizarding world after the final Potter book, though some light has been shed via the Pottermore website, as well as the Cursed Child play.

We do know that Auror and Order of the Phoenix member Kingsley Shacklebolt becomes the Minister of Magic, and one of his first actions is to banish the Dementors. The creatures had abandoned their posts in Azkaban, freed the Death Eaters, and joined Voldemort's army, after all.

Rowling has yet to reveal further details about their fate, but we can speculate that the post-Voldemort world is probably not to their liking. Aurors took their place as guards in Azkaban, and prisoners presumably are treated in a more humane fashion.

Coupled with the hope and optimism of a world free from the Dark Lord's influence, it's possible that the dark creatures are well on their way to extinction.

They Haunt The Universal Studios Forbidden Journey Ride

Harry Potter and the Forbidden Journey ride at Universal Studios

There's nothing like a good theme park, and Universal Studios earned rave reviews for its Wizarding World of Harry Potter expansion in 2010. Visitors to the park are whisked into J.K. Rowling's magical world and can explore a number of famous locations, including Hogsmeade, Diagon Alley, and of course, Hogwarts.

However, theme parks are all about the rides, so the real highlight is Harry Potter and the Forbidden Journey. Combining classic bumps and dips with special effects and even filmed performances from actors like Daniel Radcliffe and Emma Watson, it takes tourists on a magical (and dangerous) romp around Hogwarts.

One of the scarier sequences sends the riders into the Chamber of Secrets, where they're menaced by Dementors. A variety of tricks are used to make the riders feel like their souls are being consumed by the creatures before Harry finally saves the day with a Patronus Charm.

---

Do you know any other interesting facts about Dementors in Harry Potter? Let us know in the comments.