Empusa (Έμπουσα, Empousā, of unknown meaning) is a demigoddess of Greek mythology. In later incarnations she appeared as a species of monsters commanded by Hecate (known in English as an empuse).
She is often associated or grouped with the demigoddesses Lamia and Mormo, who were likewise demoted to a species of underworld demon in later mythology (the lamias and mormolyceas, respectively).
As a demigoddess
Empusa was the beautiful daughter of the goddess Hecate
and the spirit Mormo
. She feasted on blood by seducing men as they slept before drinking their blood (much like a succubus
; see sleep paralysis
Empusa is pictured as wearing brazen slippers and bearing flaming hair. By folk etymology, her name was said to mean "one-footed" (from Greek *έμπούς, *empous: en-, in + pous, foot). This gave rise to the iconography of a one-legged hybrid, with a donkey or ass leg and a bronze prosthetic leg.
Later and modern usage
In later Greek mythology, her role was reduced to a species of Hecatean demon called an empuse or empusa (pl. empusae). The empuses were sent by Hecate to guard roads and devour travelers (Hecate was also the goddess of roadsides). According to Philostratus, empuses ran and hid, uttering a high-pitched scream, at the sound of insults.
Today the term is still used to refer to a shapeshifting hobgoblin said to pester Greek shepherds in the form of a dog, ox, or mule (perhaps harkening back to the classical representation).
The empuses are best known for their appearance in Aristophanes's The Frogs, in which they scared Dionysus and Xanthias on their way to the underworld.