Vampire

Vampire (n) - Undead creature of the night that feeds on the blood of the living. First appeared in English in 1732 but dates back to a Serbian word vampir and ultimately to an ancient Tartar word, ubyr, meaning "witch."
Descriptions of vampires date back to the dawn of time. There is a story that Lilith, Adam's first wife, was a vampire. Archaeologists have dug up pottery in ancient Persia that depicted demonic creatures drinking the blood of men. Egypt, India, China, Africa, and, of course Europe all have folk tales about vampires.

Excluding Vlad Tepes (Dracula), the most famous historical figure suspected of being a vampire is Countess Elizabeth Bathory. Called the Blood Countess, Bathory was a 16th century Hungarian noblewoman who believed that she would maintain eternal youth by bathing in the blood of over 600 virgins during her life.

There are real support groups for people (undead?) who think they are vampires and are having a hard time dealing in a world filled with un-undead people.