There are two branches of Night-Children, but both stem from He’s one of the oldest living beings among the Mythos. The... More, as he was the first.
Their abilities and strengths/weaknesses vary slightly from generation to generation. You can view their terminology here.
To become one of the Night-Children, one needs to start out human, which means pure, unmagical Ever-Dying genes. (There have been exactly three exceptions: One of the Night-Children, made sometime in the She won’t ... More, One of the Night-Children, made sometime in the He won’t s... More, and Jonathan is a Night-Child, and an impossibility. More.) An exchange of blood starts the process, but the human must lose so much blood that they’re near death.
More importantly, the Night-Child must will the change to happen. Simple blood-swap is not enough to transform.
- Initially, all “baby” vampires are insane. Their hunger – which, according to He’s one of the oldest living beings among the Mythos. The... More, is called The hunger experienced by all Night-Children, or vampires. More – takes over. New vamps usually need to be locked away for a while until they can gain control of themselves again.
- All vampires, regardless of ethnicity, have green eyes after changing. It’s been referred to as “vampire green,” and occasionally, it glows.
- Vampires can make a bite feel pleasant (to put it mildly) or painful (to understate). They can also alter memory so their victims don’t recall being bitten. These are all abilities He’s one of the oldest living beings among the Mythos. The... More carefully monitors; he has a thing about consent.
- Any blood will do in a pinch, but the Night-Children need human blood. They were designed to drink it, and when deprived of it – even if given other blood – they will eventually lose control of the Beast and rip through whatever stands between them and human blood. (Fortunately, that blood-thirsty madness takes a while to form.) If after that they still cannot obtain human blood, they will eventually die.
- The blood itself can be healthy or not; human pathogens have no effect on vampires. However – and this is crucial – the blood must be from a living person. Even blood that has been donated is fine, but if the donor dies, or the person being drunk from dies, the blood becomes poisonous to the Night-Child. So far, no one is certain why, though He’s one of the oldest living beings among the Mythos. The... More thinks it has something to do with the The invisible threads which bind a soul to a body. More.
- They can all perform an ability they call “going to dust,” in which their physical forms disintegrate into what looks like dust motes, like the kind one might spot floating in a beam of moonlight. Whatever this form is, it isn’t dust. They can enter and exit even air-proofed containers in this form. However, they can’t attack; while no physical barriers can stop them, they can’t affect the physical world, either.
- Night-Children have a special relationship with the wind, largely because the wind itself seems to view He’s one of the oldest living beings among the Mythos. The... More as a friend. They say the wind tells him things – things no one else could possibly know.
- Vampires do not age. When Made, that is their physical age forever.
- They DO have a heartbeat, but it is very slow.
- They seem to have no limit to the blood they can drink, which is deeply confusing. So far, science has failed to reveal just where all the blood goes when swallowed.
- Vampires do not need a full physical form to function. While removing (or damaging) the head can kill them, it’s not a guarantee. Loss of limbs or organs or even much of the torso is no guarantee of death, either. If the vampire is able to go to dust, they will heal.
- Wood is their primary weakness. It enters their system, burns, damages, and prevents healing. If there’s too much wood in a vampire’s body, they can’t even go to dust.
- Sunlight only affects vampires far down the bloodline from He’s one of the oldest living beings among the Mythos. The... More. Usually, around the fourth generation, sunburns make an appearance. By the time we reach the tenth generation, vampires must avoid the bright sunlight or face burns.
Notte’s children follow specific rules. He forbids random hunting; there are no mad monster vampires running around on his watch. He also forbids his children from making anyone they wish, instead choosing to approve each and every human his children want to bring into the fold. Most of the time, he says no.
A vampire, and Notte’s oldest surviving child (not his fir... More runs her own family differently. She has to abide by Notte’s rules to some extent, but he gives her a lot of freedom – some say too much. Let’s just say her branch of the family is responsible for much vampire media and mythology throughout the world.
Self-control is the most important aspect of a Night-Child’s life. Because of this, the early years of vampirism are carefully and strictly controlled, down to the clothing they’re allowed to wear.
They almost never complain about it. They feel the Beast, and with very few exceptions, are well aware they need his help to keep themselves in control.