|Invisible to Muggles
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|Harry Potter and the Prisoner of Azkaban
Dementors are the guards of Azkaban Prison. It is difficult to determine what their features are, because they conceal themselves completely under flowing black cloaks.
At its first appearance, a Dementor is described as a "cloaked figure". "Its face was completely hidden beneath its hood." When we first see it, in Harry Potter and the Prisoner of Azkaban, we do see a part of it: there was "a hand protruding from the cloak and it was glistening, greyish, slimy-looking, and scabbed, like something dead that had decayed in water; the thing beneath the hood, whatever it was, drew a long, slow, rattling breath, as though it were trying to suck something more than air from its surroundings."
Dementors are dark creatures that consume human happiness, creating an ambiance of coldness, darkness, misery and despair. Because of their power to drain happiness and hope from humans, they have been set the duty of being guards at Azkaban, where they prevent the prisoners from having the will or ability to escape.
This creature has the property that only wizards can see it. Muggles can still feel them, though. Its only known ability, besides the happiness drain, is the ability to perform the "Dementor's Kiss", which is the act of extracting the human soul through the mouth, leaving nothing more than a living body. This process is irreversible.
They "are among the foulest creature 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. Even Muggles feel their presence, though they can't see them. Get too near a Dementor and every good feeling, every happy memory will sucked out of you. If it can, the Dementor will feed on you long enough to reduce you to something like itself... soulless and evil. You'll be left with nothing but the worst experiences of your life," as Professor Lupin tells Harry.
The only spell we are aware of which is able to repel these creatures, is called the Patronus charm. In Harry Potter and the Half-Blood Prince, when Harry asserts that the Patronus charm is the only way to battle Dementors, Professor Snape tells him that he is wrong; but this supposed different way of tackling Dementors is never described.
From his first exposure to them, Harry is much more sensitive to the effects of Dementors than anyone else – Harry alone, of the six people present in the train compartment, passes out when the Dementor enters to search it. Harry is very much afraid that this is a display of weakness, until just before Christmas, when he discusses the matter with Professor Lupin. Lupin explains that Harry is more deeply affected because Dementors work by extracting good memories, leaving nothing but the bad recollections, and Harry has a much grimmer history than anyone else.
In Harry Potter and the Prisoner of Azkaban, we find that Professor Dumbledore has managed to block the attempt to place Dementors inside the school, but cannot prevent the Ministry from positioning them outside the grounds, at all the known entry points to the school. Their stated purpose at that time is to prevent Sirius Black from entering the castle. One must wonder how the Ministry believed that would work, as Sirius had already escaped from Azkaban, and so must have some way of evading the Dementors. Possibly this is just the Ministry doing anything so that it appears to be doing something, as it so often does.
One also wonders why the Dementors would stay on as Azkaban guards, when there are so many people elsewhere in the world for them to suck emotion out of. Perhaps it was a mistake allowing so many of them to visit Hogwarts and discover exactly how thin the takings were in the prisoners at Azkaban, relative to the rest of the world. It is certainly true that they abandoned Azkaban with great alacrity in the middle of Harry Potter and the Order of the Phoenix.
While it is never stated, there is an implication that the Dementors are a created being, rather than one that occurs naturally. The statement in Harry Potter and the Half-Blood Prince, that the Dementors are breeding, leads us to believe that they are of natural origin. Perhaps, like guard dogs, they were created from a naturally-occurring magical creature, possibly the Lethifold, by selective breeding methods, or by means of magical enhancement of the traits in which Wizards were interested.
- In Harry Potter and the Half-Blood Prince, the Minister for Magic attributes the gloominess of the weather to escaped Dementors breeding and multiplying. Why are Harry and Ron unable to recognize this?
- Harry, at one point, "found it difficult to imagine Dementors surviving for long in bright sunlight", upon realising that Sirius was hiding out in the Tropics. Might there be any truth in this?
- What might Snape be talking about when he comments that there is at least one more spell to combat Dementors?
Although the Dementors leave Azkaban in the middle of Harry Potter and the Order of the Phoenix to join Voldemort, one has to wonder, given their earlier actions, whose side they are on from the beginning.
All through Harry Potter and the Prisoner of Azkaban, though the Dementors are nominally seeking Sirius Black, they seem to have fixated on Harry, to the point of trying to administer the Kiss to him rather than Sirius when both of them are trapped.
At the end of Harry Potter and the Goblet of Fire, the Dementor that Cornelius Fudge has brought along with him, "for his protection," administers the Kiss to Barty Crouch Jr. before Fudge can interrogate him. If the Dementors had already allied with Voldemort, this would be sensible as it would increase the delay before Voldemort's return would be made public. Of course, the Dementor could have recognized Crouch as an escaped Azkaban inmate; however, that is unlikely, as Crouch had been replaced in Azkaban by his mother some ten years previous to our story, and the substitution had not then been noticed. As up until their official defection, Dementors seem to be always under the Ministry's control, the most probable explanation seems to be that Fudge brought the Dementor with himself for precisely this purpose (in line with this, it is Fudge personally who receives the blame for Crouch Jr.'s demise by characters like McGonagall and Dumbledore).
The two Dementors who attack Harry and Dudley near Privet Drive in Harry Potter and the Order of the Phoenix are apparently under orders from Dolores Umbridge, or at least so she claims near the end of that book. There is some question at the time of the attack as to whether Umbridge was actually being controlled by Voldemort, as Harry's scar did later twinge at one point when she held his hand. Sirius, in conversation with Harry, dismisses that idea, though, saying that as bad as Umbridge is, the Order does not believe her to be controlled by Voldemort.
From the long sequence of things done by the Dementors that directly hinders the Wizarding world, one must conclude that they are more inclined to follow Voldemort than the good Wizards, and additionally that at the best of times, Wizarding control over the Dementors is very tenuous indeed. It may be an error to assume that Dementors are evil, however. It is more likely that they are amoral, possibly having insufficient intelligence to have any real concept of morality, and simply follow the main chance. Harry is targeted, not because he is Harry, but because he is, to Dementors, a better source of the energy they require than Sirius. Barty is attacked only because he is helpless and a suitable energy source (and perhaps on account of Fudge's personal offer, which a Dementor would obviously not resist). And the only reason the Dementors choose to follow Voldemort is because he frees them from their duty to Azkaban, allowing them access to the richer pickings on the mainland.
It is a shame, perhaps, that Snape never elucidates his comment about there being a better spell to eliminate Dementors. If they are breeding, as Fudge says at the beginning of Harry Potter and the Half-Blood Prince, then they will likely need to have their numbers cut down. As it is, we don't know if there is any method of effectively doing that; the Patronus charm will repel them, but we don't know of anything that will destroy them. Of course, it would be possible, if rather labour-intensive and difficult, to herd them with Patronuses into an enclosed place, making sure that no possible prey is in that place with feelings for them to feed on. If they are then prevented from escaping by being surrounded with many Patronuses, presumably they would eventually die of hunger. We cannot speculate how many wizards would be necessary to cast the necessary number of Patronuses, of course.