Vampires

Vampires (吸血鬼,) are an immortal race of humanoid beings that feed on the blood of humans. Vampires have fangs, pointed ears, and red eyes. Until drinking human blood, the vampire may age and retain his/her original eye color. Vampires do not retain strong emotions from when they were human and gradually lose more and more of their humanity. Despite being former humans themselves, vampires look down on humans and consider them nothing but mere livestock. They dislike increasing their numbers and very rarely turn a human into a vampire. A vampire's power is dependent upon age and lineage.

Drinking human blood is insanely pleasurable to them, especially right from the source. Vampires can also enjoy drinking vampire blood, but the details and limitations of this have yet to be revealed.

When a vampire is killed, he/she turns into ashes.

A vampire who starves does not die but rather becomes a demon.

Progenitors
Progenitors are shown to be the same as royalty among the vampires. All progenitors are nobles but all nobles are not necessarily considered to be progenitors. They are quite powerful, and this power increases with greater rankings. However, progenitors of the same ranking are not necessarily equal in power. Progenitors ranked 6th and better have the right to attend meetings of the Progenitor Council. It is likely that the vampire queens and kings around the world are all high-ranking progenitors of a very high lineage.

Not shown:
 * 2nd Progenitor Waldo Gilles
 * 3rd Progenitor Gable Fatima
 * 17th Progenitor Zane Lindau

Nobles
A human turned into a vampire by a progenitor becomes a noble. The nobles are high-class vampires who are far stronger than the average vampire and wield stronger weapons. There are 20 ranks of nobles.

Common Vampire
Common vampires are vampires who are not of nobility. They seem to be weaker than the higher classes, but remain stronger than humans.

Law

 * Vampires are forbidden from any meddling with the Curse of the Seraph.
 * In the city, vampires are forbidden from drinking blood directly from a human. They may only drink blood directly while on the surface or on the battlefield.
 * Only Progenitors are allowed to turn a human into a vampire, proclaimed to reduce the population from growing. However, it can be observed that this law is ignored often due to the abundance of common vampires.

Aging
A newly-turned vampire can survive off of their sire's blood and will continue to age until drinking human blood, but this will only work for a limited period of time. Once the vampire drinks human blood, their biology stops completely, and the vampire grows tremendously in strength and power. By drinking human blood for the first time, a vampire evolves into a true vampire.

Natural Abilities
Vampires have impressive power and regenerative abilities; this increases with their lineage and age. Nobles have the authority to turn a human into a vampire if they so choose.

Weapons
In battle, they use their natural abilities as well as different types of weapons. Second-Class weapons are used by Common Vampires, and are not as powerful as First-class weapons. First-class weapons pierce a Vampire's hand to drink their blood in order to significantly increase their power. It appears that there are two levels of 1st class weapon usage with a visible difference between the two: a spiked vine or spikes piercing the entire hand.

It is unknown what resides within 1st Class weapons that drinks the owner's blood, but the mechanism is very similar to vampires themselves and demons (who crave blood as well).

They can also power-up by drinking human blood at any time.

Weaknesses

 * They have immense pride and typically underestimate their human opponents or may refuse to work together with vampires of rival factions.
 * 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.

Trivia

 * They refer to the humans as "livestock" or "humans" instead of calling them by their names. With an exception of Ferid Bathory as he used to call Mikaela Hyakuya by his name while he was still human.
 * Yūichirō Hyakuya reads a book in chapter 1 that erroneously tells him vampires are merely 7x as strong as humans and require arm bands to go into the sunlight.
 * Many female vampire nobles have small horns.

Reference
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