The nghrau species has been present on the world for most of human existence. The nghrau and humans are of a different species and therefore are unable to interbreed. In fact, it is rare that nghrau are able to breed at all; nghrau pregnancy is dangerous and almost all cases result in the death of the mother, the offspring, or even both.
The nghrau feed off the life essence of living creatures, regardless of whether they are undead or a living being. Nghrau do not need blood in order to feed although it is faster to ingest another's essence by doing so. The nghrau subsist by feeding in order to remain energized, physically fit, and alive. Nghrau that refuse to feed off others will slowly (and quite literally) shrivel up and die.
If in the sun, a nghrau will irreversibly and uncontrollably age at a rapid rate (about a year for every minute) and could potentially die because of it. Other than prolonged exposure to the sun, the only other known way to kill a nghrau and have them stay dead is by decapitation. Able to fly, nghrau are extremely vulnerable while in flight and therefore tend to keep their feet on the ground.
A being that is born a nghrau ages by regular but limited exposure to the sun. It is said that a born nghrau who is exposed to the last few seconds of daylight at sunset every day for thirteen years will grow up to be very healthy and strong. A nghrau child that is exposed to sunlight at varying intervals or for too long will grow up weak, too quickly, or both and is therefore easier to kill or could even die before it has fully matured.
It is possible but rare that a being can become a nghrau. To become a nghrau one must feed off the blood of a nghrau which can be extremely dangerous and even fatal for both parties. It isn't uncommon that a being dies instantly upon ingesting the blood of a nghrau due to the painful, slow, genetic transformation they undergo.
( Nghrau History: )