In ancient Greek mythology, Empusa was the beautiful daughter of the goddess Hecate and the spirit Mormo. She is credited to be the first vampire-type creature in western mythology. However, similar creatures were common in eastern traditions (e.g., Chinese, Hindu) centuries before Empusa made her first appearance.
According with Greek traditions, Empusa feasted on blood by seducing young men. After climax, her victims would fall deep asleep and she would drink their blood and eat their flesh. When in human form, Empusa was pictured as an irresistible young woman with flaming hair, always wearing brazen sandals.
In Roman times, Empusa stopped being a demigoddess to become a roaming specter-type being, or better say, group of beings. The Empusae (plural of Empusa) devoured unsuspected travelers, leaving their bones at crossroads to frighten the unwary. They were described as having shape-shifting abilities, preferring the shape of a strix (owl) to travel fast at night, but that of a young woman to attack.
According to Philostratus (Lucius Flavius Philostratus, a Greek philosopher of the Roman imperial period), the best way to protect yourself from an empusae attack, was to insult them, for they ran and hid, uttering a high-pitched scream, at the sound of foul language.
The empusae are best known for their appearance in Aristophanes's The Frogs, in which they scared Dionysus and Xanthias on their way to the underworld.
Over time, however, the term empusae became a general word to describe nocturnal demons associated with sleep. Because the empusae fed while her victims sleep, they were credited with producing the sleep paralysis phenomena, and in medieval times, they became associated with the Succubus, as depraved entities that liked to prey on innocent sleeping men.
-Zelenyj, A., 2012. SEEING EVIL. Back to Frank Black, p.249.
-Parsons, C.O., 1977. The Refining of Lamia. The Wordsworth Circle, 8(2), pp.183-192.