Vampires

Vampires (吸血鬼,) are an immortal, ageless race that feeds on the blood of humans. All vampires were originally humans who were turned when ingesting vampire blood although they like to pretend otherwise and look down on young vampires as "former humans."

Appearance
Vampires are exquisitely beautiful creatures with fangs, pointed ears, and red empty eyes; however, vampires have methods of changing their appearances. For instance, Saitō appears with normal ears and wears colored contacts to mask his eye color. Their blood is dank and black though in the anime it's red.

They have no body heat, pulse, or bodily excretions since their metabolism has utterly stopped, and never grow age.

Incomplete Vampire
A human that ingests the blood of a vampire does not become a vampire but rather an incomplete vampire. The only known incomplete vampire in the series is Mikaela Hyakuya. Newly-turned vampires can survive off of the blood of the one who sired them, but this will only work for a limited period of time.

Like true vampires, incomplete vampires will grow fangs as well as  in strength, have no heartbeat, and  their ears become pointed; however, they are weaker than true vampires of equal rank, retain their human eye color, and continue aging until they drink human blood which then turns them to true vampires.

Despite incomplete vampires not being true vampires, true vampires seem to have no aversion towards them as Mika is seen alongside them several times, and they seem unperturbed by the prospect of an incomplete vampire working with them.

Nature
After a human ingests vampire blood, they lose their emotions until only the greatest components of their personalities remain in addition to their everlasting thirst for blood; they also have no sexual desire or any other desires, aside from the craving to drink blood. Due to their loss of emotions and desires, many vampires try to make themselves interested in something in order to stave off their eternal boredom, but vampires concerned with anything other than blood are considered to be eccentric. Krul Tepes and Ferid Bathory are considered to be eccentric, and Mikaela Hyakuya even more so. Although they have no need to sleep, they may do so to take a break from eternity. They typically sleep between early morning and noon. It is unknown who started this, but many vampires sleep in coffins since they are comfortable to vampires and help hide them from sunlight.

Vampires typically band together out of their own self-interest and not out of affection or love for one another, and they have no qualms about killing their own allies once they lose their human feelings. They may choose to sire a human to keep as a companion to ward off the boredom of eternity; however, many show aversion to spreading their curse and may try to use another noble to turn the person they designate. Should they sire a vampire themselves, that vampire will always be much weaker than them in power.

As hemovores, they can only ingest blood and nothing else, and the better the blood tastes, the stronger the urge is to drink that person to death. Additionally, human blood tastes best when that person is at the throes of death. At first, they may originally feel guilty about killing humans and drinking their blood, but they gradually come to consider them nothing but food after decades of feeding on them and watching the humans foolishly wage war with one another and repeat the same mistakes redundantly.

They can generally resist their thirst for blood for only three days at most before losing control, and consider biting and drinking a human dry to be the greatest pleasure. Vampires can also enjoy drinking vampire blood, but the details and limitations of this have yet to be revealed as the only example is Mika, who lived off of Krul Tepes's blood for four years before it is no longer effective at quenching his thirst.

A vampire who starves does not die but rather becomes a demon. A vampire may also become a demon if their heart is removed from their body and can be prevented by returning the heart to the vampires' chest. Cutting off a vampire's head using normal weaponry will not kill a vampire, although it will render the vampire unable to use his or her body. When a vampire is killed, their bodies becomes ash.

Origin
Currently not much is known about the origin of vampires. What is revealed is first mentioned in the Prologue of Book 1 of Seraph of the End: The Story of the Vampire Mikaela where the angel Michaela fell to the earth demanding God to give them blood.

Progenitors
Progenitors are royalty among the vampires. All progenitors are nobles, and a human turned into a vampire by a progenitor becomes a noble. Nobles are far stronger than the average vampire and wield superior weapons. There are twenty ranks for nobles. The progenitors with the lowest number have the highest rankings. By default, they are extremely powerful and higher ranks even more so. However, progenitors of the same rank are not necessarily equal in power. Sixth Progenitors and above have been sired by the First Progenitor and have the right to attend meetings of the Progenitor Council. It is likely that all vampire monarchs are progenitors of an esteemed lineage.

The rank of progenitor corresponds with the number of progenitors holding that rank. For example, there is one First Progenitor (status unknown), two Second Progenitors, three Third Progenitors, and so on. In total there are 19 progenitors in the Progenitor Council (excluding the first progenitor and Saito).

A vampire always holds a rank weaker than his or her sire. For instance, a vampire sired by a Seventh Progenitor would not be able to have a rank greater than a Thirteenth Progenitor or a vampire who is sired by the 2nd progenitor would not be able to have a rank greater than a seventh progenitor.

Not shown:
 * 17th Progenitor Zane Lindau

Common Vampire
Common vampires tend to be weaker than the higher classes but remain stronger than humans. A common vampire with greater battle prowess has influence similar to a lower-ranked noble.

Laws

 * Vampires are forbidden from any meddling with the Seraph of the End. Violation will result in imprisonment for all eternity.
 * Prior to the Apocalypse, vampires were forbidden from meddling with human affairs. This law was overturned once the human population became threatened, and vampires rose up to save their food supply.
 * In Sanguinem, vampires are forbidden from drinking blood directly from a human. They may only drink blood directly while on the surface or on the battlefield. This is because more vampires tend to drink their prey dry than not. However, laws are determined by the vampire rulers of each city and may vary even within the same country.
 * Drinking blood from another vampire is taboo but grants immoral pleasure.
 * Only nobles are permitted to turn a human into a vampire.
 * According to Ferid, vampires are not allowed to use another vampire's blood to turn a human into a vampire. If they do so, both the sire and the young vampire will be subjected to imprisonment for all eternity.

Punishment

 * The most severe punishment for a vampire is imprisonment deep underground for all eternity. Since a vampire's brain will continue to regenerate, the prisoner will forever long for blood without any way to fulfill that desire and any ability to die.
 * Another severe punishment for a powerful vampire is torture by exposure. By exposing the vampire to direct sunlight without a UV-protective armband, the vampire will burst into flames and scream in agony.

Natural Abilities
Vampires have impressive power and regenerative abilities; this increases with their lineage and age. They can easily reattach a limb. It is also possible to reattach a vampire's head, although the vampire in question will need someone to bring the two ends of the neck together. Nobles have the authority to turn a human into a vampire if they so choose. Vampires may increase their abilities by drinking human blood at any time.

Their senses are extremely powerful, and their eyesight allows them to distinguish a target several hundred meters away, even in pitch-black darkness. However, they no longer perceive anything as beautiful.

Weapons
In battle, they use their natural abilities as well as different types of weapons. First-class weapons pierce a vampire's hand and drink vampire blood in order to significantly increase their power. Their nature is unknown, but they have existed prior to the 1300s.

Second-class weapons are used by common vampires, and are not as powerful as first-class weapons.

The weapons enhance their own physical abilities as well.

Protective Gear
Vampires most commonly wear armbands on their left arms to protect themselves from UV light. They may also wear rings. This allows them to move under sunlight without harm, although they still dislike it. In Book 2 of The Story of Vampire Michaela, Ferid becomes distressed and groggy during daytime when his ring malfunctions.

Technology
The vampires have advanced technology compared to the humans and comment when human technology becomes advanced. Ferid takes notice of it when he first comes across a Horseman of John in Book 2 of Guren Ichinose: Catastrophe at Sixteen. During the Progenitor Council meetings in Vampire Reign, the vampires talk to each other across the world through video.

Weaknesses

 * They have immense pride and typically underestimate their human opponents or may refuse to work together with vampires of rival factions.
 * Sunlight Exposure to UV light will create a toxin in their bodies, and vampires must wear protective gear to neutralise this effect. Otherwise, they will burst into flame. Even with the protective gear, they disdain the sunlight, but they can tolerate it.
 * Daytime. Without protective gear, vampires are too tired to function during the day time, as shown by Ferid Bathory in The Story of the Vampire Michaela book 2.
 * They can be killed if their heads are destroyed. One bullet will not do the job.
 * Cursed gear and enchanted gear used by the Japanese Imperial Demon Army limit their healing capabilities
 * Removing their heart will weaken them and begin to turn them into a demon.

Trivia

 * They typically refer to the humans as "livestock" instead of calling them by their names.
 * Yūichirō Hyakuya reads a book in chapter 1, which states vampires are 7x as strong as humans. Considering a vampire's ranking, this can be a severe underestimation.
 * Krul, Chess, and Horn either have small horns or horn-like decorations on their heads.
 * Any vampire is capable of turning a human, but their laws only give permission to progenitors.
 * Sixth progenitors and above have all been turned into vampires by the First Progenitor.
 * Only sixth progenitors and above may attend a Progenitor Council meeting under normal conditions.
 * Abnormal conditions include when a lower-ranking vampire is reporting on the battlefield or a lower-ranking vampire is the vampire of highest authority in a region.