Dementor

"Dementors are among the foulest creatures that walk this earth. They infest the darkest, filthiest places, they glory in decay and despair, they drain peace, hope, and happiness out of the air around them... Get too near a Dementor and every good feeling, every happy memory will be sucked out of you. If it can, the Dementor will feed on you long enough to reduce you to something like itself...soul-less and evil. You will be left with nothing but the worst experiences of your life."

- Remus Lupin to Harry Potter

A Dementor is a Dark, soul-sucking fiend. They served as the guardians of the Azkaban until the Battle of the Department of Mysteries, when Lord Voldemort was sighted in the Ministry of Magic and their defection to his side was realized.

Description
"They sort of freeze your insides, don't they?"

- Fred Weasley on proximity to Dementors

Dementors have a humanoid shape, approximately three metres in height, but covered in dark, hooded cloaks which reveal only grey, decayed hands and faces. They have no eyes, only a large hole where the mouth should be, which is used for sucking the soul out of the victim in a process called the Dementor's Kiss, which is generally considered worse than death. They are said grow like fungi in the darkest, dankest places, creating a dense, chilly fog. Unlike other creatures, who move through some means of physical support, Dementors can fly freely, without support. Being blind, Dementors sense and feed on the positive emotions of human beings to survive, forcing them to relive their worst memories. The very presence of a Dementor makes the victim's surrounding atmosphere grow cold and dark, with increasing effects as the number of Dementors rise. Those kept in the company of a Dementor for too long become depressed, and are often driven insane, which is the main source of Azkaban's well-deserved horrible reputation.

"They don't need walls and water to keep the prisoners in, not when they're trapped inside their own heads, incapable of a single cheerful thought. Most go mad within weeks."

- Remus Lupin on Azkaban prisoners' long-term exposure to Dementors

Their source of sustenance allows the Ministry of Magic to reluctantly employ them: Dementors are at least intelligent enough to be greedy, and to obey as long as doing so provides them with sustenance. In 1995, a Dementor accompanied Cornelius Fudge as a bodyguard, and Dementors are depicted as obeying simple instructions from wizard authorities (e.g. escorting prisoners into and out of the courtroom), but the precise extent to which wizards and Dementors can communicate with each other is unclear. Possibly Dementors react to raw emotion rather than to actual spoken words.

Although Muggles cannot see Dementors, they are affected in a way similar to wizards and witches, becoming depressed. While at least one Squib, Arabella Figg, has claimed to see a Dementor, it was later found out to be a lie.



Protection from Dementors
One of the few ways to shield oneself from Dementors is to use the difficult Patronus Charm to drive them away. The charm summons a Patronus: the magical manifestation of good will, providing varied levels of protection against the Dementors' influence, based on the caster's strength as a wizard. Only when summoned by an experienced caster will the Patronus take the form of an animal significant in some way to the individual. While the lower level Patronus is more amorphous and ephemeral, corporeal Patronuses will chase down Dementors and force them to flee the vicinity. An incorporeal Patronus can only slow a Dementor down, as if the creature is walking through quicksand, and tends not to last long. Chocolate is an effective first aid to mild cases of contact.

Dementor's Kiss
In addition to feeding on positive emotions, Dementors can perform what is known as the Dementor's Kiss, in which a Dementor latches its mouth onto a victim's and sucks out the person's soul. The victim is left as an empty shell, incapable of thought and with no possibility of recovery. It is believed existing after a Dementor's Kiss is worse than death: as a person's soul is their self, to be "kissed" by a Dementor is to cease to exist, and yet also remain. The Ministry of Magic occasionally allows this as a punishment.

Muggles who have had their souls sucked out in a Dementor's attack would mistakenly be thought to suffer from the medical condition known as Persistent Vegetative State by Muggle doctors, since after the 'kiss' the victim would no longer experience any brain activity, despite no damage done to the brain itself. This makes Dementors even more terrifying, since they will attack both wizards and Muggles alike. It is unknown what effect a Dementor's Kiss will have on a person who has split his or her soul through use of a Horcrux.

The only known Kiss occurred in 1995; Barty Crouch Jr., who had been working in secret for Voldemort, was restrained at Hogwarts for a trial. His soul was sucked out by a Dementor accompanying Cornelius Fudge.

Harry Potter's Encounters with Dementors
"When they get near me -- I can hear Voldemort murdering my mum."

- Harry Potter on the Dementors' effect on him

Harry Potter first encountered Dementors during the school year of 1993-1994, when they were sent to guard Hogwarts School of Witchcraft and Wizardry against Sirius Black, who had recently escaped Azkaban. Harry, whenever he got near one, was forced to relive his worst memory: hearing the last moments of his parents' lives before they were murdered by Lord Voldemort. The first of these encounters was on the Hogwarts Express, during which he was protected by the new Defence Against the Dark Arts professor, Remus Lupin. While the Dementors were at Hogwarts, Headmaster Albus Dumbledore warned the students not to give the Dementors any reason to harm them.

Harry endured a second encounter with a group of Dementors during a Quidditch game, which caused him to lose consciousness and suffer a fall from his broom. He was that time rescued by Dumbledore, who slowed Harry's fall then drove the Dementors away with a Patronus. They seemed to be particularly attracted to Harry because, due to his miserable childhood and many bad memories, he was particularly vulnerable to their influence.

To overcome the Dementors, Harry asked Professor Lupin for assistance. Lupin taught Harry the Patronus Charm, which took the form of a stag, just like that of his father. Harry initially failed to produce a fully formed Patronus when he and Sirius were attacked by a group of Dementors. The two were saved by the intervention of a powerful and fully formed Patronus, which had in fact been conjured by Harry himself, who travelled back in time with Hermione Granger by use of her Time Turner. (This technically counts as both Harry's third and fourth encounters with the Dementors, since, due to his time traveling, he experienced this same encounter twice.)

Harry's fifth encounter was in an alley near his home on Privet Drive, when he and his cousin Dudley Dursley were ambushed by two Dementors, sent secretly and illegally by Dolores Umbridge. He was able to successfully use the Patronus Charm and was subsequently rescued by a Squib named Arabella Figg.

During the Battle of Hogwarts, the Dementors fought on the side of Lord Voldemort and the Death Eaters. Harry and his friends were attacked by large numbers of them, and due to the horrific events they had experiences and witnessed, including the recent death of Fred Weasley, they all had difficulty summoning their Patronuses. Seamus Finnigan, Luna Lovegood, and Ernie Macmillan drove them off with the charm.

Separation from the Ministry
The Dementors served the Ministry of Magic as the guards of Azkaban because it allowed them to feed on the emotions of the prisoners. However, by July 1996, most of the Dementors of Azkaban staged a mass revolt against their employers to join Lord Voldemort, who offered them more victims. This aided the 1996 and 1997 escapes of Death Eaters from Azkaban.

By mid-1996, the Dementors who had joined Voldemort were multiplying, thus causing an "unseasonal" July mist. Cornelius Fudge also admitted they are factors in the British Prime Minister's recent decline in terms of public approval, as they were making people less happy in general. Professor Snape also requested a report on Dementors, when Harry disagreed with Snape on the method for confronting a Dementor. One could interpret this to mean there is more than one way to repel a Dementor; this is likely given that most Dark Wizards are apparently unable to produce a Patronus Charm.

When Kingsley Shacklebolt became Minister for Magic following the Second Wizarding War, Dementors were no longer used by the Ministry of Magic, presumably because they were deemed untrustworthy and inhumane.

Behind the scenes

 * In an interview on March 24, 2008, Rowling revealed that the inspiration for Dementors came from her bout with severe depression prior to her phenomenal success. She described as an "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."
 * The name Dementors likely comes from the words dement, "to make insane", and tormentor, "one who afflicts with great suffering".

Appearances

 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (film)
 * Harry Potter and the Prisoner of Azkaban (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows

Notes and references
Détraqueur