Vampires

Vampires are a race of humanoid being that feed on the blood of the Humans. The Vampires despite being former humans themselves look down on the 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 depend on their numeric for being a founder, as shown when the third Founder, Kururu Tepes easily defeated 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 a livestock become a noble due being turned by the third Founder, Kururu Tepes. The Nobles are powerful as Michaela was shown to be powerful enough to kill a Horseman of The Apocalypse with ease, thought this may be the result of him being turned by the third founder.

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

Law
The Vampires world have laws similar to the Humans world. One of these laws is that the Vampire World is forbid any meddling with 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 were shown not different than they were four to six years ago. However, Michaela Hyakuya who was turned into a Vampire four years ago was shown to have aged and look like the same age as his friend Yūichirō Hyakuya. The reason for this is unknown, wither it is a special case or a trait for Vampires in this universe and they stop aging in a current age is yet to be explained.

Trivia

 * Vampires most of the time refers to the Humans as livestock instead of calling them by their names or just calling them Humans.