The Hungarian, Elizabeth Bathory was born in 1560 to George and Anna Bathory. She is known as the countess who tortured and murdered more than 600 victims.
Elizabeth was raised at the Bathory family estate at Ecsed in Transylvania. She grew up at a time when much of Hungary was a battleground between the Turks and the Austrians. As a child, she suffered from seizures accompanied by intense rage and uncontrollable behavior.
In 1574, Elizabeth became pregnant to a peasant man, and was sequestered until the baby was delivered because she was engaged to marry Count Ferenc Nadasdy. They were married in May of 1575, but Count Nadasdy was a soldier and was frequently away from home for long periods of time, so Elizabeth took on the responsibilities of managing the affairs of Sarvar, the Nadasdy family estate.
During that time period, it was common for those in power to treat their servants cruelly, but Elizabeth was uncommonly cruel. She would find excuses to inflict punishment and torture mostly upon young servant girls. She would stick pins in various sensitive places on the body, such as under the fingernails, and during the winter, she would execute victims by having them strip, led out into the snow, and then would pour water over them until they were frozen.
Elizabeth's husband would join in occasionally and sometimes actually teact her new forms of torture, such as in the summer, having the victim stripped, covered with honey, and then left to be bitten or stung to death by various insects.
Count Nadasdy died in 1604, and Elizabeth began to spend time at her estate at Beckov and at a manor house in Cachtice, both of which are located in present-day Slovakia. Her main partner in the sadistic behavior was Anna Darvulia, but Anna died in 1609, and Elizabeth turned to Erzsi Majorova. Majorova encouraged Elizabeth to include a few noble women as her victims, and so she killed a young noble woman and called it a suicide.
Sometime during the summer of 1610, an initial inquiry had begun, and on December 29, 1610, she was arrested. During her trial, a register with the names of 650 victims was found in Elizabeth's living quarters. She was sentenced to life imprisonment in solitary confinement and spent the rest of her days in a room in her castle at Cachtice. She died on August 21, 1614.
She is considered a true vampire not because she drank blood, but because she would bath in it to keep her skin youthful. It was said that one day when she was having her hair combed by a servant girl, the girl accidently pulled her hair, so Elizabeth slapped the girl and some of the blood got on Elizabeth's hands. When she rubbed it on her hands, they seemed to take on a youthful appearance, and thus brought about her reputation for desiring the blood of young virgins.
Apparently, Bram Stoker also used some of her characteristics as a basis for his Dracula. Originally, the novel was to take place in Austria (Strigia) not Transylvania. Also, Dracula became younger and younger as the novel progressed, which alludes to Elizabeth becoming younger by bathing in blood.
Information from The Vampire Book: The Encyclopedia of the Undead - by J. Gordon Melton