Vampire

Vampire (吸血鬼) is the general term for those who suck the blood of humans; it includes the blood-sucking species that is the Dead Apostles as well as those that aren't Dead Apostles. While it can be synonymous with the Blood-sucking species, the term Vampire generally refers only to those hunted by the Church. In the Tsukihime setting, vampires have the instinct known as "vampiric impulse," which pushes them to suck the blood of others. But differently than the vampiric impulses of the True Ancestors, who are also considered vampires, these vampires have the physical need to suck the blood of others, in order to maintain their own bodies. However, if the vampire gives the human his own blood in the process, the human body will not completely die and the soul cannot leave the body. In most cases however, the body dies and with it the soul of the victim and the final result is an empty corpse, that the vampire can control like a puppet, called the Dead (死者). But sometimes, there are those whose body possess an above-average life force, which prevents the body and with it the soul from dying. After several years in the grave, the brain dissolves and the soul is freed from the cage of the body; and it becomes a Ghoul (食屍鬼). How far the newly created Bloodsucker will evolve is then decided by the magical potential of the body which is stored inside the soul.

The Ghouls and their transformed souls, can bypass the necessity of the brain to hold the soul, as their soul is now separate from the body. They have mental capacities pretty much equivalent to that of a savage beast and they must devour other corpses to reconstruct their own degenerated flesh. And those who have successfully restored their bodies and thus, their brain, can be called Living Dead (リビングデッド). They are inferior to The Dead in terms of raw strength but the fact that they regained their own will and can maintain their own soul, puts them on a different standing than a mere puppet. After a few more years, the living dead can fully recover their intelligence and mature to a Dead Apostle (死徒). The actual time, it takes, to complete this Growth Process is at least a hundred years.

Those who became Vampires can move on their own free will, but they cannot escape the rule by which they have to supply blood to their vampire parent. After growing accustomed to living in darkness after some more decades, the vampire still follows his vampire parent but can give their own blood to a human and have their own followers. A vampire can only become a full-fledged Dead Apostle after breaking free from the control of his parent vampire. To stop that eternal cycle, the Church has built the Burial Agency, to hunt heresy and destroy the Dead Apostles. The purpose of the Burial Agency is the extermination of all vampires as well as the sealing of the founding 27 Ancestors. When a Vampire dies then it won't leave a trace behind as their bodies turn into ash.

Source: Tsukihime Dokuhon PlusPeriod dictionary entry (p.178)

This term is used more loosely with magi that obtained vampire-like properties through their magecraft, and it looks to be more of label of how much is such property considered dangerous to other people. Matou Zouken is not considered a vampire by the Church even though he is possessing and eating the bodies of other people with his Crest Worms to sustain his life and is even called a vampire on one occasion, albeit as an insult, while Nrvnqsr Chaos is considered a Dead Apostle, despite the fact that he doesn't really drink blood but merely absorbs entire human (and animal) bodies as organic material. Difference is in scale: in normal circumstances, Zouken needs one body every few decades, while Nrvnqsr on one occasion devoured all residents of a hotel (over one hundred people) in mere minutes.

Types of vampires

 * True Ancestors
 * Demon Lords are fallen True Ancestors who succumbed to their blood thirst and became a threat both to humans and the Ancestors themselves. As they no longer needed to suppress their thirst, they could employ their powers to their full extent and therefore vastly overwhelm their still restrained kin. It was with the purpose of their elimination that the Ancestors caused the birth of Arcueid Brunestud. By the time of Tsukihime, all of them had long been eliminated. It should be noted that despite the name, they are not to be confused neither with the demonic ethereal beings born from human belief, nor with the oriental demons of Japanese folklore known as Oni.
 * Dead Apostles
 * Living Dead
 * Ghoul
 * The Dead

Curse of Restoration
True Ancestors and Dead Apostles possess a form of limited immortality, called the Curse of Restoration. This ability operates under normal conditions and causes the vampire's body to regress through time to its original vampiric state whenever it receives an injury. However, this ability is also tied to the phases of the moon. As the moon waxes, the degree of injury that can be repaired, as well as the speed of the regression increases dramatically. For example, Roa would not have been able to survive Arcueid's Marble Phantasm, were it not for the full moon. Additionally, is the night of a full moon the time when the Dead Apostles and True Ancestors reach the height of their strength.

Source: Tsukihime Dokuhon PlusPeriod dictionary entry (p.178)