Lady of Blood: Countess Bathory

Finally, the crop of peasant girls had run out. Erzsébet, ever daring, turned her blood thirst to lesser aristocrats. She had done so much thus far without being stopped, and like many serial killers after her, arrogance made her bold and stupid. She was eager to extend her reach for the thrill of seeing what she could get away with. She also appeared to be so caught up with the pleasures of what she was doing that she could not stop. 

Sabine Baring-Gould, an English author and folklorist of considerable status during the 19th Century, used the tale of Erzsébet as an example of his own view of a certain psychological phenomenon. I have seen an accomplished young woman of considerable refinement and of a highly strung nervous temperament string flies with her needle on a piece of thread, and watch complacently their flutterings, he wrote in 1865. Cruelty may remain latent till, by some accident, it is aroused, and then it will break forth in a devouring flame. He says that the passion for blood follows the same pattern. We have no conception of the violence with which they can rage till circumstances occur which call them into action... passion blazes forth, and the serenity of the quiet breast is shattered for ever. A word, a glance, a touch, are sufficient to fire the magazine of passion in the heart, and to desolate for ever an existence.

Blood thirst, too, may lurk inside a person, even those we love, and we may never even spot it. It may smolder in the bosom which is most cherished by us, and we may be perfectly unconscious of its existence there. Perhaps circumstances will not cause its development; perhaps moral principle may have bound it down with fetters it can never break.

To replenish her diminishing stable, Erzsébet offered to teach social graces to young women from noble families, and when they arrived at the castle she had her pick. After the murder of one of such young lady in 1609, which Erzsébet tried to stage as a suicide, the authorities finally decided to act. This suspicious incident, coupled with the many other rumors over the years, required action. The king supported it, because Erzsébet had been asking him to repay funds he had borrowed from her husband, and if the rumors proved true and she was arrested, he would be free of his debt. In other words, everyone would win... except the lady in question.