Vampires

Vampires are a race of humanoid beings that feed on the blood of Humans. The Vampires, despite being former humans themselves, look down on humans and consider them mere livestock.

Founders
Founders are shown to be the same as Royalty among the Vampires. They are quite powerful and their power depends on their number placement for being a Founder, as shown when the Third Founder, Kururu Tepes, easily severed the arm of the Seventh Founder, Felid Bathory.

Nobles
The Nobles are high class Vampires whom apparently were turned by one of the Founders as Michaela Hyakuya, a former human whom used to be livestock became a noble due to being turned by the Third Founder, Kururu Tepes. The Nobles are powerful as Michaela was shown to be strong enough to kill a Horseman of The Apocalypse with ease; though this may be the result of him being turned by the Third Founder.

Common Vampire
Common Vampires are Vampires who are not Founders or Nobles. They seem to be weaker than the higher classes, but remain stronger than humans.

Law
The Vampires' World has laws similar to the Humans' World. One of these laws is that the Vampire World is forbidden from any meddling with rhe Curse of the Seraph.

Aging
The Vampires are shown to be immortal and ageless as the Founders Kururu Tepes and Felid Bathory and one of the Nobles, Lacus Weld, showned no disernible sign of change from their image four to eight years ago. However, Michaela Hyakuya who was turned into a Vampire four years ago was shown to have aged and looked the same age as his friend Yūichirō Hyakuya. The reason for this is due to Michaela's refusal to drink human blood, thus preventing him from turning into a true vampire.

Trivia

 * Vampires most of the time refer to the Humans as "livestock" instead of calling them by their names or simply "Humans".