Vampires are a sort of creature known only to a very few scholars and theologians in the Genosian world. The idea of these creatures is thoroughly suppressed where possible, and what remains of them to the common folk are only rumors, confused legends and folklore.
But vampires are very real, and very dangerous. There are two varieties, the Lesser, and the Greater or "Star" Vampires.
Lesser Vampires are bestial creatures that thirst for the blood of sentient beings. They are solitary, savage, and while cunning and intelligent, it is an alien and inhuman intelligence that cannot be communicated with meaningfully.
Lesser Vampires are bipedal, but in no way resemble humans. Their faces are eyeless, marked only by a circular lamprey-like mouth lined in sharp teeth, and both their hands and feet are prehensile with six vicious claws. By itself, the Vampire is a fast, powerful, and deadly adversary that heals quickly from its wounds and can heal quicker still by absorbing the blood of a slain victim.
But that is not what makes them so fearsome. Vampires have a very acute sense of smell, and can detect heat using strange pits on their eyeless faces. But more than that, they have supernatural powers. A Vampire can travel through mirrors as though they were doorways, mimic human voices with perfection, and (in a limited sense) read the surface thoughts of humans from a distance. Some of them can psychically hypnotize their victims so that they do not make noise as they die.
Combined, a Vampire's abilities allow it to prey on humans with terrifying efficacy, and one Vampire can easily remain undetected in a human city for decades, eating regularly. What is worse, its victims frequently reanimate as the undead, which though not hostile to the Vampire are not under its control.
These are just lesser Vampires. The difference between them and the Star Vampires is the difference between a baboon and a man.