Dementors are semi-intelligent non-beings who were previously employed by the British Ministry of Magic, with their job being Guards for Azkaban Prison. Dementors were dismissed from their post entirely by Minister Kingsley Shacklebolt after the Second Wizarding War due to their change of allegiance during the war. It is unknown where these spirits went after being dismissed. Dementors are not loyal creatures, and they will align with whoever provides the largest group for them to feed on.

This dark spirit can be easily recognised by its appearance, which resembles something similar to a wraith. They glide at around 12ft tall with a basic humanoid frame and arms, but they do not have legs. Dementors are wrapped in a weathered black cape which hides most of the spirit's body. A Dementor's face is nearly entirely hidden by its hood, but underneath would be two empty eye sockets and a dark hole where a mouth should be. Any skin that is exposed on the creature's body - such as their hands - appears decayed, slimy and scabbed, with ashen grey skin.

Even if a Dementor is not instantly seen, their presence in the atmosphere is powerful enough to alter it. They draw anything positive or warm out, leaving even Muggles - who cannot see them - feeling chilled. They cause feelings of depression and even despair, as people genuinely forget in that moment how to feel happy. When targeting a person, they suck out the happiness and force their victims to live out their nightmares again and again. The most dangerous ability a Dementor has is called the 'Dementor's Kiss' which involves the creature sucking out a person's soul. This is normally the only time a person would see underneath their hood, as that black mouth is used to extract the soul by clamping onto the victim's mouth. A person who has had their soul removed is left alive, but an entirely empty shell. It is deemed a fate worse than death.

The Dementor's empty eye sockets are not just a visual trait; these spirits are blind and act on sensing emotions from a person or even emotions in the atmosphere, but this is deeply inaccurate, and they have been known to target the wrong person at times.

A witch or wizard can protect themselves against Dementors by casting the Patronus Charm. As these creatures feed on living happiness, a patronus charm is something that they cannot feed on due to the fact it is not alive. The simple consumption of chocolate helps restore a person after an encounter with a Dementor.