Vampires (吸血鬼 Kyūketsuki) are a species of supernatural beings in High School DxD.
Like the Devils, Vampires are residents of darkness that have existed since ancient times. They have similar rankings and weaknesses like that of High-Class Devils. However, Devils are residents of the Underworld, while Vampires are beings that live in the darkness of the human world. They may seem similar, but their views and culture differ greatly.
The Vampires are a race of supernatural creatures even more proud and aloof than the Devils. In fact, the discrimination between Vampires and other species is so strong that it has reached the point that Dhampir, like Gasper and Valerie, who were born from Vampire Lords and human mothers, are treated badly even by their own family members.
Several hundred years ago, there was an incident that split the world of Vampires, where the Vampires argued between choosing a female true ancestor and a male true ancestor in order to retain pure-blooded Vampires. This incident eventually gave birth to the Tepes Faction (ツェペシュ派 Tepeshu-ha), a male dominated Vampire faction and the Carmilla Faction (カーミラ派 Kamīra-ha), a female dominated Vampire faction. Both factions became at war with each other after the Tepes Faction recently got hold of a Longinus possessor.
Vampires do not get along well with other races and have a strict, pure-blooded aristocracy who are so arrogant that not even a single family has ever cared about their servants even a tenth of much as the Gremory family has cared for their servants. Also, any Vampire with a human in their parentage, whether humans-turned Vampire or are descended from one, are never allowed to become nobles and considered substandard members of the species, assuming that they're even considered Vampires in the first place.
However in Volume 16, it shows that some Vampires went against their pure-blood principals and sought enhanced body modifications, the modifications turned out to be part of Rizevim's plan to turn the into mass-produced Evil Dragons as reinforcements. Later on in Volume 21, the remaining Vampires joined the anti-terrorist group DxD, with both the Tepes and Carmilla Factions putting aside their differences and battle together, possibly indicating to now have a different viewpoint towards other races than before.
While physically similar to humans, Vampires have beautiful doll-like faces, with a set of sharp fangs in their mouths and a pair of red eyes. Pure-blooded Vampires have no reflections on mirrors, lack shadows, and have a corpse-like skin tone.
While the full extent of their abilities have never been entirely explained, some Vampires are known to be able to control bats, transform into a flock of them, and use them for reconnaissance.
They can also gain more power by drinking the blood of certain beings, such as when Gasper drinks Issei's blood.
Their very presence also creates a cold aura that can be felt by others several meters away, even while inside a building that the Vampire is outside of. In Volume 15, it is revealed that Vampires are also able to create and manipulate fog, often using it to create barriers and search for enemies. High-Level Vampires can create enough fog to blanket an entire town. Vampires can also manipulate shadows and darkness.
Being creatures of the night, Vampires are weak against sunlight. Vampires also need to drink blood occasionally to stay alive. Vampires are beings that can’t enter buildings which they haven’t been invited to come in. They cannot walk across running water and hate garlic. Like Devils, Vampires are also weak against objects related to the Church, such as crosses and holy water. They also can't heal themselves unless they sleep in their coffins.
A Female-dominated Vampire Faction. The Carmilla Faction have a principle of Women commanding more power than men.
A Male-dominated Vampire Faction. The Tepes Faction have a principle of Men commanding more power than women.
The Dhamphir are hybrids of Vampires and other species. These type of Vampires have all basic Vampire powers but are immune to their weaknesses such as the effects of sunlight, although they do still seem to feel some discomfort.