|“||Demons are beings that serve the Devil.||”|
Demons are malevolent, inter-dimensional beings that travel between worlds, destroying everything in their path. They return to their home dimension, the Void, when they die in their corporeal form. Religiously, they are defined as Hell's denizens and the servants of Satan.
Demons come in a large variety of species and forms, their numbers said to be infinite.
The term "demons" is the generally accepted word used to refer to the creatures that Shadowhunters fight because of the varying terms and concepts among different belief systems and world cultures among mundanes, Shadowhunters, Downworlders, and even angels. Jonathan Shadowhunter utilized the term based on his own religious history.
In the Earth dimension, demons take different forms, though it is unknown whether it is their true form. Demons are easily recognizable unless they are shapeshifters. Almost always taking on monstrous appearances on Earth, demons can also usually be discerned by the uncanny, nauseating feeling that bellows around them like a dark aura. In addition to their general hideousness, demons often carry with them a debilitating scent of death that can be very strong.
Demons' bodies are kept fresh and alive by ichor. Their ichor, infused with demon energies, is black with a slight green tint. It is viscous, as opposed to the golden blood of the angels, and is thinner than human blood yet opaque. While ichor is not generally dangerous, it is somewhat toxic, and some are acidic and can burn what it touches. While the usual range of protective Marks protect Shadowhunters from this, many demons are still poisonous, wherein the healing rune iratze is ineffective.
Demons are powered by roiling demon energy, a vitalizing spark that maintains their form in the corporeal dimension, as opposed to souls of other beings. When demons die, this energy is separated from its physical body and will return to its home dimension, Hell; others, particularly Greater Demons, are shattered into pieces and scattered in between worlds, taking them centuries to reform.
To the human eye, their disappearance can take many forms, depending upon their type. Some explode or burst into dust, some fade from view, while others crumble into themselves. Some leave behind ashes or smoke, depending on the manner of its death. In all cases, however, no remnant of the demon's physical self remains in the corporeal world. Warlock rituals exist that can "preserve" demonic physicality in the corporeal world, allowing one to collect and keep such a thing as a vial of demon blood without its vanishing when its demon source is dispatched. An example of a container for demons is the Pyxis.
Demons live on pain and suffering, on the cries and agony of the damned in torment. Demons also take pleasure in feeding on happy memories freely given to them by humans—memories that disappear from the person's mind once devoured by the demon—which they usually gain in exchange for favors, such as when they are summoned.
One of the most powerful magic that demons possess is their ability to take possession of a human's body, though this is very rare and usually only done by very powerful Greater Demons. The only way the connection between the possessor and the possessed can be broken is by killing the demon, which could also kill the possessed.
Most common demons cannot speak human languages. A large number of types are, however, able to parrot human speech that they have heard. This is often a sign that a demon has been summoned rather than coming to Earth on its own. There are a number of demon languages that the Nephilim and warlocks have identified and learned, including Abyssal, Chthonic, Purgatic , Gehennic, and Tartarian.
The most immediate weakness of demons is their vulnerability to angelic power and heavenly fire. However, like the Downworlders they brought into being, they cannot easily, or permanently, be harmed by normal earthly weapons. As such, most Shadowhunter weapons are Marked to strengthen them against demons.
In addition to being repelled by direct seraphic energy, seraph blades being the most used, most demons can be warded off with holy symbols of all kinds. While holy objects or places cause violent reactions or sometimes harm in ordinary demons, they only result in slight discomfort in very powerful demons. Like vampires, demons also cannot stand the direct force of sunlight, though they can stand artificial lights with no ill effects.
Moreover, demons are, in some form, living creatures and are vulnerable to physical harm. Falling off from high places, getting buried in a rockslide, getting crushed under large objects, like chandeliers, grand pianos, and roof collapses, will kill the demon even if the objects aren't Marked with runes.
Though demons are able to detect the presence of other demons and Downworlders, they are unable to perceive the difference between mundanes and Shadowhunters and are unable to sense the workings of angelic magic. This enables Shadowhunters to hide from them using glamours. Sensors can also detect the presence of demons, and most demons are distinguishable and easily detected because of their rotting garbage stench.
- Main article: Demon pox
Astriola, most commonly known as demon pox, is an infection contracted by Nephilim through inappropriate relations with a demon, or a person infected with the disease. If untreated, it will inevitably result in the demonification of its bearer. Mundanes are immune to the disease. Shadowhunters are presumably prone to it because of their angelic blood.
The true origin of demons is unknown, though common belief is that demons "serve the Devil." It is believed that the fallen archangel Lucifer created and rules demons and turned Lilith into the first demon. Lilith, in turn, created more demons. While the more mythological story is that she scattered drops of her blood on the ground in the land of Edom, according to sources made available to the Conclave, demons were created after the angelic fall first appeared on the Earth during the travels of Lilith and her partner Sammael. The demons were soon banished by Heaven, from Earth to the Void.
"Lesser demons" is the term used to refer to the demons with no identity or intellect and which are so common that they fall under a particular species or classification.
Demons that have distinctive identities and personalities but have not been referred to as Greater Demons. Some may be "minor demons".
- The blue-haired Eidolon demon that Clary saw Jace and the others corner and kill in the Pandemonium Club.
- A huge, humped and massive demon with an armored body and many limbs, with each of its appendage ending in a spiked chitinous talon. It has huge and splayed elephant feet. It has the head of a giant mosquito, complete with insectile eyes and a dangling blood-red feeding tube. It screams like a human and is very, very strong.
- A demon that resembles a huge, awkward bird. It is an ugly, flying creature that resembles a pterodactyl, with wide, leathery wings and a bony triangular head. Its mouth is full of row upon row of serrated shark teeth, and its claws glint like straight razors. It has no eyes, only indentations on each side of its skull. The wings end in blade-sharp ridges of bone.
- A demon that looks like an animated skeleton, with a bloodied hatchet clutched in its bony hand.
- A scaled, lizard-looking demon with rodent teeth and black claws.
- A demon in Edom that feeds on dreams and wishes of a person's heart and projects these into an imperfect illusion into a person's mind to deceive them, keeping them unconscious in the real world by keeping them in a false reality.
- The Whitechapel demon that is known as Jack the Ripper in mundane history. This demon is considered to be a Greater demon.
- Several other demons at Benedict Lightwood's party.
- Some demons are known to be employable, by mundanes, Downworlders, and even Shadowhunters.
- Sabnock's sibling — an Eidolon demon that was a gift to Horace Dearborn. It later confronted Julian Blackthorn at the battle of the Cohort's parley in the shape of Annabel Blackthorn.
- The Shadowhunter's Codex
- City of Heavenly Fire
- City of Lost Souls
- Demons and weapons — Cassandra Clare on Tumblr
- City of Bones
- Clockwork Prince
- Chain of Gold
- Lord of Shadows
- The Red Scrolls of Magic
- What Really Happened in Peru
- A Lightwood Christmas Carol, a Chain of Gold extra
- TLH 2021 calendar — Cassandra Clare's October 2020 newsletter
- City of Ashes
- City of Glass
- The Whitechapel Fiend
- "I'd say greater" — Cassandra Clare on Twitter
- What to Buy the Shadowhunter Who Has Everything
- The Mortal Instruments
- Queen of Air and Darkness