Vampire

To a Vampire they are the apex of human existence- the sublime, immortal union of spirit and flesh. Mortals are merely flawed reflections of this perfection, suitable only for recruitment into the ranks of the eternal, or fed upon as chattel. When a possessing spirit bonds with a living body, it becomes a vampire. This can happen if a Ghosts possesses a victim for too long, thereby destryoing its original spirit, or when a Hollow is specially prepared for the purpose by ancient ritual. 
Scholars of the arcane say that vampirism breaks the chain of being. Over time, a vampires spirit essence diffuses fully into the body, giving it physical immortality while at the same time destroying its echo in the spirit realm "beyond the black mirror". Some have argued that this is the only wayt o escape the damnation of madness that otherwise inflicts all the ghosts denied passage through the gates of death. 
Vampires are exceedingly rare today, most people considering them to be legendary or mythical. In the 6th Century of the Imperium a vampirism movement achieved significant popularity before it was eradicated by the Spirit Wardens. When the Spirit Wardens do discover one, they take great pains to destroy it in secret so as not to disturb the peace. In legend, vampires were destroyed by the rays of the sun. Since the sun was shattered by the cataclysm, this is no longer possible. Spirit wardens must capture the vampire and disintegrate it in electroplasm according to a specific arcane method in order to destroy it. 
A vampire sustains its energy by feeding on life essence from a living being. In fables vampires drank blood to accomplish this, but this is not typical. Each vampire feeds on essence in its own way- leaving a distinct telltale sign on its victim afterwards. A vampire can easily detect these signs in order to locate their victims again for feeding, or to take care to avoid feeding on the chosen prey of another vampire. 
The powers and flaws of vampires often manifest differently across all of the individual vampires across the world. Some might be able to sense things beyond human limits, hearing a subjects true thoughts and feelings or seeing in pitch darkness. Others are able to perform superhuman feats of strength and speed, leaping onto rooftops, breaking stone with their bare hands. Unbeknown to most mortals some vampires are invisible to spirits and can walk the streets with people turning a blind eye to their presence. With these strengths, a vampire may also have unique flaws, unable to enter private residences without permission from the owner, repelled by spiritbane charms, bound to their host body or their body twisting into horrific bestial forms when they are harmed. Along with myths of blood and sunlight, the need to enter a deep slumber has some semblance of truth, with some vampires bound to this habit to maintain their forms.