The Department for the Regulation and Control of Magical Creatures: Dementors; information classified by The Ministry of Magic.
Dementors
Dementors are possibly the most iconic monsters of the Harry Potter series. An original creation, there is little in mythology that relates to them exactly, but they have quite a strong symbolic background nonetheless.
Their nature almost precludes them from proper biological and ecological analysis.
Almost.
The symbolism of dementors is quite blunt and blatantly obvious—and they wouldn’t be nearly as effective if it wasn’t. Dementors are severe, clinical depression: the kind that eats away at a person and leads to quiet suicides, the sufferer believing that no one will notice their passing. Their lack of specific weaknesses, besides positive experiences, similarly links them to depression. You don’t kill depression, you drive it away and keep it at bay—unless you have a giant robot capable of punching holes in reality or know a Kryptonian or two who can punch entropy, that’s the best you can do.
In the films, their design is molded after withered corpses in burial shrouds, but with a lamprey-like, yet toothless mouth for sucking the joy and souls from their victims.
Many ethereal, sometimes undead, creatures that feed on the life force or vitality of an individual can be found in mythology, though the diet of joy is quite rare outside perhaps an errant Japanese Gaki which can feed on such odd things as life force, virility, tattoos and incense. As a byproduct, they seem to suck the heat from their immediate surroundings.
Among folkloric monsters their bizarre feeding practices would actually classify them as a variety of vampire.
To be specific, it actually fits into a class of folkloric vampire called the Psychic Vampire or Energy Vampire—often talked about by occultists.
The spirit being variety of these creatures are invisible ghost-like entities that feed on the energy, vitality or sexual energy of the target. Humans who claim to be energy vampires often feed on a specific type of energy: “creative energy”, fear, happiness, rage, sex, suffering—any emotion, really. Just depends on the type.
None of these humans in this world have have claimed the James Randi Paranormal Challenge’s million dollar prize money, so take that as you will.
Dementor Biology
Dementors are a phylogenetic nightmare. Reproducing through spores and budding (“Like a Fungus” to quote the author), they have a mouth but no apparent anus, but have a humanoid shape.
The movies gave us a shot of a hypogryph excreting dung, so that’s a fair assumption given their other biological quirks.
For their feeding strategies, we’re going to have to science up some magic.
Which means there’s only one call we can make…
Yes, we’re going to be using Ghostbusters’ physics to describe these guys.
Given that all magic in media and fiction tends to act as psycho-reactive substances and, like most magical media, it draws its inspiration from the spiritualist movement of the early 20th and late 19th centuries, it’s not as daft as you might initially think.
That these creatures float like ghosts in the books (as opposed to flying in the films), treating them like ghosts is a pretty good base to work from.
Dementors, however, appear to be physical entities, at least in the films.
They cannot phase through walls and use magic to open doors. They may feed on emotional energy (IE: psycho-reactive ectoplasm in Ghostbusters terms), but their bodies are solid. With no anus (since most ghostly creatures just taper off at the waist), they probably sweat their waste from their entire bodies as a deterrent to most predators.
A lot of animals use their anal secretions as a defense against predators, so it’s actually no that bizarre a trait.
Further, they react physically to these manifestations of emotional magic, either fighting or being pushed away by it. These spells have the consistency of gelatin in most appearances, so the overall displayed reaction follows logically.
Dementors are described as feeding on joy and happiness and in the books, patronus charms (spells which create specters of concentrated joy) are used to first slow down, distract and, at their strongest, fight the dementors.
In the films, it’s used more to drive them off, which does clash with their description as joy-feeders. If a patronus is joy, then why would they be driven off by a good quantity of their food? A way to look at it and have it make sense is that it drowns them in joy. Sure, you can drink water, but too much water and you’d drown. This ties into their ectoplasm-sensitivity, reacting to the things normal matter can pass through.
Dementors are also shown to devour “souls” with their ‘kiss’, leaving the target alive but “hollow” and emotionally dead.
Of course, writers never really define what a soul is within their works, but fret over it nonetheless. Usually it ends up as a memory-emotion matrix unique to a person.
It’s likely that the soul is their true target, and their normal emotional-draining attacks are actually attempts to slowly tear out the soul from the body (a bit seen in the film version of Prisoner of Azkaban).
The books make a token reference to other methods of driving them off, but none of killing them. This has led many fans to believe they are immortal in the same sense as deities—un-killable and eternal.
Fans are quite fond of the “No Limits Fallacy.” Characters in comics, like Doomsday, are written like that. Doomsday has the ability to mutate himself to overcome whatever stopped them before. Whenever Doomsday appears in media forms, this aspect is dropped for the simple reason that it’s extremely silly and quite unbelievable to most audiences. Still, a lot of hardcore fans go and apply this thinking mentality to their favorite series/monsters and it is almost always ludicrous.
One of the only exceptions, of course, being the Wolfman from the film Monster Squad which shows what happens if anything other than silver bullets is used.
Dementors, however, are not an exception.
Creatures that are un-killable and breed rapidly are, well, that kind of puts a cramp on any attempt at a happy ending no matter how you slice it. They’ll just wait and breed until nothings left.
Speculation time:
What keeps dementors in check besides good vibrations?
First ask: What eats fungi?
Second ask: What habitat requirements do they have?
In nature fungi are eaten by a wide variety of invertebrates. Slugs and similar slow moving, ground animals are out, but it’s likely that their greatest enemies are insects. The Prisoner of Azkaban established that they can’t really sense animals that well due to the insect’s primitive minds they’d be easy prey for parasitoid beetles, gnats and other insects. Unknown to wizards, those are probably their greatest banes—tiny bugs which use the Dementors as nests to create new life, which slowly devour the monsters from the inside out, leaving them empty husks.
One of the tidbits picked up about dementors is that there are none in the tropics. This may mean that their cold-abilities has limits and can be overloaded. This can possibly show signs that fire or heat can act in a similar method to a patronus at minimum or just burn them up. The design taken for the movies makes them even more flammable.
Which is a call back to older magical traditions, fire is seen as the ultimate cleanser of supernatural evils.
Burning dementors works well in that light.
