Dementors

Dementors are foul, soul-sucking non-beings considered to be among the darkest creatures in the wizarding world. They feed on human happiness, and thus cause feelings of depression and despair in any person in their vicinity. Lacking true loyalty, they are driven by their singular desire to consume positive emotions. For many years, they served the Ministry of Magic as the guards of the wizarding prison, Azkaban. Their most terrifying attack is the Dementor's Kiss, which rips a person's soul from their body. The only known defence against a Dementor is the Patronus Charm.

Dementors are amortal creatures that breed in the coldest, darkest places. For centuries, they infested the island where the fortress of Azkaban was built, making it their natural habitat. When the Ministry of Magic decided to use the fortress as a prison, they chose to allow the Dementors to remain as guards, a decision that provided immense security at a terrible cost to the prisoners. Their first significant appearance in the series occurs when they are dispatched to guard Hogwarts and search the Hogwarts Express for the escaped prisoner Sirius Black. During this time, one entered Harry Potter's train compartment, causing him to faint. Their presence around the school throughout the year had a profoundly negative effect on Harry, prompting him to learn the advanced Patronus Charm from Remus Lupin. In the summer before Harry's fifth year, two Dementors were sent to Little Whinging, where they attacked Harry and his cousin, Dudley Dursley. This was an unauthorized attack, secretly ordered by Dolores Umbridge to discredit Harry. Shortly after Lord Voldemort's return to power, the Dementors abandoned Azkaban and allied with him, as he could offer them a far greater scope of victims than the Ministry. They subsequently fought on the side of the Death Eaters during the Second Wizarding War, including at the Battle of Hogwarts. Following Lord Voldemort's defeat, the new Minister for Magic, Kingsley Shacklebolt, officially ended the use of Dementors at Azkaban, a major reform for the wizarding world. (Pottermore)

Dementors are large, humanoid figures, approximately human-sized, and are covered in dark, tattered black cloaks that obscure their faces. Their bodies are described as being greyish and decayed, and their visible hands are “glistening, greyish, slimy-looking, and scabbed.” They move with a silent, gliding motion. They are blind, as they have no eyes. Beneath their hoods lies a formless face with a large, gaping hole for a mouth, which is used to perform the Dementor's Kiss. They radiate an intense, unnatural cold that can freeze moisture in the air. Dementors do not possess a personality in the human sense. They are instinct-driven beings motivated solely by their need to feed on positive human emotions. This single-minded hunger makes them unreliable allies, as they will abandon any master who cannot provide them with sufficient “food.”

• Aura of Despair: A Dementor's primary influence is passive. Their mere presence drains all happiness and warmth from the surrounding area. Victims are forced to relive their worst memories and are overcome with a feeling that they will never be cheerful again. Prolonged exposure leads to deep depression and madness.
• Dementor's Kiss: This is a Dementor's ultimate attack. By clamping its mouth onto a victim's, it sucks out the person's soul, leaving them in a permanent vegetative state—an empty, living shell without memories, personality, or self-awareness. This fate is considered to be worse than death. The Ministry of Magic authorized this “punishment” for Barty Crouch Jr..
• Flight: Dementors can glide over the ground and fly through the air, allowing them to pursue targets effectively.
• Emotional Sensing: Being blind, Dementors sense and track humans by feeding on their emotions. This allows them to navigate and find victims, but it can also be a weakness. Sirius Black was able to escape Azkaban by transforming into his Animagus form; as a dog, his emotions were less complex, confusing the Dementors.

• Ministry of Magic: For a long period, the Ministry had a symbiotic, if dark, relationship with the Dementors, employing them as the highly effective guards of Azkaban. This arrangement ended when the Dementors defected to Lord Voldemort, revealing their lack of true allegiance.
• Lord Voldemort and Death Eaters: The Dementors were natural allies for Voldemort, whose reign of terror promised them an endless supply of fear and despair on which to feed. They willingly joined his forces, swelling his army and serving as instruments of terror.
• Wizards and Muggles: Dementors are universally feared. They affect Muggles just as they do wizards, though Muggles cannot see them in their true form, instead perceiving a chilling fog or a feeling of sudden dread. The only effective defence against them is the Patronus Charm, a difficult piece of magic that few wizards can perform successfully. They seem to have less effect on Squibs like Arabella Figg, who can feel their cold but are not overwhelmed in the same way.

The name “Dementor” is closely related to the English word “demented,” which means to be suffering from dementia or to be driven mad. This stems from the Latin verb dementare, “to drive out of one's mind.” The name accurately reflects their effect on those exposed to them, particularly the prisoners of Azkaban.

• J.K. Rowling has stated in interviews that the concept of Dementors was born from her own experience with clinical depression before her success. She described depression as “that absence of being able to conceive that you will ever be cheerful again. The absence of hope.” (J.K. Rowling interview)
• In the film adaptations of the books, Dementors are depicted as more skeletal, wraith-like beings that fly swiftly and aggressively. Their cloaks appear to be part of their bodies rather than clothing. (film)
• In the Harry Potter and the Prisoner of Azkaban video game, Dementors can be temporarily frozen and immobilized using the Freezing Charm, Glacius. (video game)