|“||The Night Children are a wise and careful people. Any scheme that draws their ire draws my suspicions.||”|
Vampires, also known as the Children of the Night, are a species of Downworlders. Along with werewolves, vampires are humans infected with a demon disease. However, unlike the former, vampires are considered "undead".
Vampires generally tend to look pale, sallow, and thin, though this is not always the case.
The blood of vampires shimmers bright red. Vampires cannot shed tears; instead, it is blood that leaks through their eyes. Being reanimated corpses, they do not have a heartbeat and do not need to breathe, although they are still able to inhale and exhale oxygen, in order to utilize their heightened sense of smell, to pass as human, or to blow on something. Their lack of breath makes them impervious to such things as asphyxiation, drowning, or gases. 
A vampire and a sire also have some sort of connection. Particularly, upon the death of one's sire, a vampire will experience a momentary jolt of pain, presumably feeling the same pain their sire felt at death.
The dirt of the grave where a vampire was buried holds special properties for that vampire. The vampire can tell if the grave has been disturbed. Vampires may use this to communicate simple messages, even without the other's presence—for instance, breaking a container of a vampire's grave dirt could be used to alert and summon that particular vampire. Clans sometimes even have a spot where a jar of every member's grave dirt is hidden, used for emergency purposes for when a leader needs to call on all their vampires.
Like werewolves, they possess superhuman strength, grace, and speed, and are able to heal quickly from most mundane injuries. They also have enhanced senses—smell, sight, and hearing. They can easily adjust their eyes to seeing in the dark, as well as almost instantly adjust when shifting between light and dark. Vampires also gain sharper eyesight than humans, and any fledgling who wore glasses in life will no longer need them as a vampire.
Vampires also have the power of the encanto—the ability to mesmerize and essentially control others. They can also shapeshift into bats, rats, and dust, while maintaining their intelligence in any form.
Power from a sire—the one who gave them the vampire blood that enabled them to turn—is also seemingly shared or transferred to some extent, mainly because it is through blood that vampires pass their powers to each other.
Vampires are resistant to large temperature differences due to their undead nature. Extreme heat no longer matters to them. However, extreme cold does not affect them either. Vampires can also cope with physical exertion and deprivation much better than mundanes or Shadowhunters.
Vampires can climb something quickly and skillfully.
|“||It is how we are made. We are drained, blooded, and buried. When he digs his own way out of a grave, that is when a vampire is born.||”|
A human who has been bitten—with the transformative properties of vampire saliva able to Turn them—or has consumed enough vampire blood, known as a fledgling, will not abruptly Turn into a vampire. To be reborn, the human must first die a mortal death, during which the undead body will enter into a state of transition. They must then be buried, during which they will reanimate while in the ground, and then must make their way out of their own grave to be 'truly born'. They must then feed on an exceptional amount of fresh human blood within the next 24 hours to complete the transition, or else they will fade and die. Because of the vampire blood, the demon "disease" and energy, and saliva in their bodies, their corpses are kept intact and animated.
Because of this, a killed fledgling should have someone familiar with the process to support the fledgling and ensure a smooth transition, specifically by being present for the vampire's rising, to ensure that the fledgling would successfully rise of the grave, and supply him or her with blood and take him or her to a safe place to recover.
The demon strain that causes vampirism can cause uncontrollable aggression, mostly associated with their thirst for blood. An orphaned fledgling—one with no guidance or clan to support it—will have little to no idea about what's happened to it, and won't know how to feed safely or even to stay out of sunlight. The importance of a clan is highlighted because of these instances, and in case this doesn't happen immediately, a Praetor is dispatched to a spotted new vampire to help.
Blood is the main component of a vampire's diet; all vampires need to drink some kind of blood for their survival. Whether it is the blood of humans or animals is up to the vampire. Mundane food can make a vampire sick since they cannot digest it, although some have learned to eat food with practice, most of which they have to spew out sometime after.
Vampires possess retractable razor-like fangs that extend from their upper canines when their blood lust is roused. These fangs are sharp and strong enough to penetrate the skin and vein of their prey. Drinking blood brings a rush of energy and vitality to the vampire. Experienced vampires can resist this rush and stop drinking to keep their prey alive, while new vampires may have trouble controlling their urge. Controlling hunger and the sheathing and unsheathing of one's fangs on command is also a feat harder to master with younger vampires.
After the initial sting of a vampire bite, the vampire saliva, which acts as a muscle relaxant and a euphoric, will dull the pain and may even make the experience pleasurable for the victim. Their saliva is believed to increase the red blood cell count of a person once in their bloodstream, making the bitten human stronger, healthier, and able to live longer; the effect is small, but it alleviates the effect of their blood loss, and so a bitten human, as long as left alive, usually remains unharmed. A well-Marked Shadowhunter can retain his or her consciousness much longer than a mundane, though there is still a heavy risk associated with being bitten.
When a vampire decides it wants more than a snack and wants a human subjugate, also referred to as darklings, the vampire will start feeding its bitten human small amounts of vampire blood to keep it docile and connected to its "master". Subjugates worship the vampire that bit them and love serving them; all they want is to be near them. They follow their every command and find offense when others speak badly of their masters. Most darklings continue serving their master in hopes of becoming vampires themselves once they die.
Along with other Downworlders, vampires are generally unaffected by mundane drugs or alcohol they ingest. However, if they drink the blood of a drugged or intoxicated human, they become drugged or drunk themselves and may become susceptible to addiction.
If vampires have not drunk blood for a long period of time, they become very pale, so that their veins look dark on their light skin and are easy to see. If they haven't had blood for too long, they become wild beasts that attack indiscriminately from hunger. Older vampires, however, can delay this process longer than younger vampires.
Vampires can no longer eat, but can still drink many things, even if only blood feeds them. 
Fire: Vampires are extremely vulnerable to fire; though they are strong and durable, their bodies are weaker and less resistant to burning.
Holy items: Holy water and other common blessed materials such as angelically aligned swords are harmful to vampires and will scorch and burn their flesh. Holy, religious symbols—like a crucifix, a Bible, etc.—may be harmful to them if they hold weight for the target vampire, depending on their belief system while still mundane. Most new vampires, with religion in their life, are not able to speak holy names such as God's, but older vampires gain the ability through years of practice, Vampires can even train themselves to resist the pain caused by these religious names and objects. If a vampire did not ascribe to a religious faith as mortals, they do not develop an aversion to holy symbols and names.
Sunlight: Vampires cannot stand the direct light of the sun. A ray of sunlight will burn the skin of vampires and cause blisters to appear on their skin. Full exposure to the sun will cause them to burst into flame dramatically, quickly reducing them to ash. It would take walls to protect vampires from sunlight, while layers of cloth will simply be penetrated through by the light. For this reason, vampires are normally careful to remain dormant and inactive during daylight hours. Artificial light, such as that of gaslight or electric light, may cause discomfort in vampires if it is strong enough, but they are normally able to remain undamaged unless already very weak. Witchlight, being light of angelic origin, may harm vampires to a lesser extent than sunlight.
An exception to this are "Daylighters", or vampires who are invulnerable to sunlight. While there used to be more Daylighters during ancient times according to Lilith, they have become rarer over time, and the precise way how they are made is unknown. One of them, Simon Lewis, became one after being fed Nephilim blood, particularly Jace Herondale's, who has more angel blood than most of his kind.
Wooden stake: Stakes crafted out of oak and piercing through a vampire's heart will slay them instantly.
Silver: Toxic to vampires and causes them to experience pain, headaches, and nausea, though it will not kill them.
Cutting off a vampire's head or bleeding them dry are among the ways to kill them.
The first vampires were said to have been created in 1444 A.D. in a public ceremony. The Greater Demon Hecate was summoned in a massive blood-based sacrifice held at the Court of Wallachia (modern-day Romania). Its then ruler, Vlad III, had a great circle of prisoners of war impaled on tall wooden spikes. In exchange for this sacrifice and act of savagery, Hecate transformed Vlad and a large majority of his court into the first vampires.
Spread of Vampirism
Vampirism did not spread seriously until a few years later when Vlad led a series of raids into neighboring Transylvania. There, he and his men gorged themselves on the blood of their enemies and spread vampirism through the entire region. Cluj became the site of the first vampire clan officially recognized by the Clave, and Transylvania took over as the epicenter of the vampire epidemic. Vampire activity in Wallachia diminished to near silence after Vlad's death.
War with the Nephilim
Simion the Scribe of the Cluj Institute in the late 15th century provided a detailed record of the original spread of the vampire plague. He described an all-out war between the Nephilim and the earliest vampire clans, with mundanes being taken from their beds and left drained in the streets, and vampires chained to the ground in village squares and left to burn in the rising sun, and other such acts.
Shadowhunters, especially those already experienced in hunting Downworlders, traveled to Transylvania for the sole purpose of vampire slaying; new vampires began to appear just as fast as old ones could be killed. Within months, the Cluj Institute, formerly one of the smallest and least important Institutes in Europe, had become the epicenter for the largest demonic epidemic the mundane world had ever seen. Chaos arose, as neither Nephilim nor vampires yet understood how new vampires were made or how they could be reliably killed.
The war ended with no clear victor. Knowledge of the vampiric disease grew, vampirism spread to other parts of Europe, and Shadowhunters returned home to sign treaties with local vampire clans and keep the peace in their own territories. Transylvania remained a devastated battleground for hundreds of years, where mortality rates for both vampires and Shadowhunters remained the highest in the world, and where the authority of the Clave was tenuous at best.
Only with the unofficial end of the Schism in the first half of the eighteenth century did the battle die down, and today the Cluj Institute is, while more vampire-focused than most other Institutes, no busier or more dangerous than any other, and Shadowhunters visit not to wage war but to see the Muzeul de Vampiri, where magically animated wax figures re-create the carnage of five hundred years ago.
Exposure, the practice of binding vampires outside to be burned by the sun, was banned in the Third Accords of 1902 after the popularity of Bram Stoker's 1897 novel Dracula, the titular character being based on Vlad III, which led to an enthusiasm for hunting and brutally killing innocent, Law-abiding vampires.
Because of the healing properties of vampire saliva, it is not against the Law for a vampire to drink blood from a human, provided that the human remains alive.
Nevertheless, the risk of accidentally killing a human has led some to refrain from drinking directly from living victims and instead drink animal blood or pre-drawn blood.
Vampires around the world may choose to band together and form a group of vampires, usually called a clan. There are several vampire clans throughout the world, with at least one or more in every major city. Usually though, no matter what clan they are affiliated with, vampires consider each other, to some extent, brethren. Clan wars do occur, however, and during these battles, leadership may change because, as with werewolves: Whoever kills the head of a vampire clan becomes its leader.
Along with faeries, vampires are committed to notions of honor and etiquette. They take bonds very seriously, as well as oaths and vows. Blood-oath rituals, as in vows written and signed in blood, bind and compel vampires, and can only be violated when broken by another ritual.
Because of the continued antagonism between vampires and the Nephilim, vampires, according to Jem Carstairs, sometimes Turn a Shadowhunter as a joke. Because of the Shadowhunter's past and heritage, the Shadowhunter will be scorned and shunned among the vampire community.
For some reason, vampires and werewolves also have a long-standing rivalry with werewolves, considered their mortal enemies. Maia Roberts once explained that the demons that passed on the disease to humans that gave birth to vampires and werewolves were mortal enemies, and that prejudice was passed down through their races.
From as early as the 1780s until as late as the 1850s, the vampire Marcel Saint Cloud led the most powerful clan in Paris. During his reign, Marcel threw blood parties, resulting in a period of "vampire craze", during which several children and young residents were made subjugates. Because of this, Downworlders chose to stay away from Paris during that time, as Marcel often asserted power over them, and Paris, to a large extent, was considered the terrain of the vampire.
A clan was existent in London during the Victorian era and led by Alexei de Quincey until his untimely death in 1878. Before this though, de Quincey led the clan liberally, secretly encouraging them to defy what he saw as the oppressive Covenant Law. During the raid on one of his parties, the Shadowhunters murdered several of the vampire members; de Quincey was later executed, with his few remaining followers. Whether the clan recovered from this is unknown.
In New York, primarily Manhattan, a clan is existent as of 2007. The clan resides in the Hotel Dumort. This clan has motorcycles that can fly through the demon energy that runs them. Formerly led by Camille Belcourt, and temporarily by Raphael Santiago, briefly by Maureen Brown, and currently by Lily Chen.
- To mundanes, vampires have no scent, but to Simon and his vampire senses, some vampires smell like metal.
- Clary, Isabelle, and Simon had got the impression that Simon looked much prettier as a vampire than as mundane. It is unknown whether it is canonical that vampires become prettier through their transformation, or whether it is a subjective assessment of the three.
- Daylighter vampires can still sleep better during the day than at night. Even if they don't mind the sunlight anymore, they feel the attraction of the night and the desire to live in the shade. Because the night is their natural time.
- Most animals avoid vampires because they instinctively sense that they are undead and also feed on blood.
- Vampires are immune to the virus that causes lycanthropy; so if bitten or scratched by a Werewolf, they will not Change.
- The Shadowhunter's Codex states that vampires have no reflection, but Simon could see himself in a mirror. So one of them is a canonical mistake.