Vampires, also known as the Night Children, are a subspecies of Downworlders. Vampires are considered "undead"—a reanimated dead human.
A human who 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 'reborn'. 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 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.
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. To feed, their retractable razor-like fangs are deployed from their upper canines when their bloodlust is roused.
Vampires, like werewolves, 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 track others through scent. Vampires also gain sharper eyesight than humans, and any fledgling who wore glasses in life will no longer need them as a vampire.
Vampires are several times stronger and faster than they ever could have been in life. New vampires must learn to control their new strength, lest they hurt others unintentionally. They can also move with such unnatural celerity that they appear as mere blurs of motion; crossing large distances in mere seconds.
One of the main trademarks of vampires is their immortality; their souls are preserved within their own animated carcass and they no longer physically age or decay, though they possess some characteristics of the dead, such as their pale and cold skin.
Vampires may band together and form a clan. As with any organization, there are politics involved and leaderships and loyalties may shift. Clans also typically align themselves with the Clave and conform to the Accords—sometimes dubiously, if small loopholes can be found—to maintain peace and remain undisturbed by Shadowhunters.
It is against the Accords to feed directly from humans. Blood should typically be from blood bags, which many Downworld establishments and clans have supplies of. However, some vampires may have secret, illegal vampire dens where they keep around subjugates, which is a direct violation of the Shadowhunter law. Bleeder dens, where mundanes willingly go to be fed on to feed their addiction to their blood, falls somewhat into a gray area as long as no one gets hurt, killed, or Turned.
Though vampires are sterile and cannot bear children, the new vampires they sire are considered by some to be their children. A vampire has a connection with his/her sire. One such connection is having the same blood running through their veins.
Their immortality does not make them immune to other forms of death.
Vampires are extremely vulnerable to the sun as well as fire. A ray of sunlight will cause blisters and burns on a vampire's skin, but full exposure to the sun or being exposed fully to unblocked sunshine will cause them to explode. A known exception to this are Daylighters, who are immune to forces that would typically destroy his kind, such as the sun and the Soul-Sword.
The dirt of the grave where a vampire was buried holds special properties for that vampire; thus, it is often well-protected. 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.