The Erinyes tormenting a criminal.
The Erinyes, also known as the Furies, were female chthonic deities of vengeance; they were sometimes referred to as "infernal goddesses". A formulaic oath in the Iliad invokes them as "those who beneath the earth punish whosoever has sworn a false oath". Their number varies, but most commonly there were said to be three. Each one was sometimes represented as avenging a certain type of crime, such as murder, marital infidelity, or patricide. The Erinyes are well known for being relentless and persistant for they will not rest until they have caught the perpatrator nor will they cease until the culprit is broken in mind, body, and soul.
The Erinyes live in Erebus and are more ancient deities than any of the Olympians. Their task is to hear complaints brought by mortals against the insolence of the young to the aged, of children to parents, of hosts to guests, of householders or city councils to suppliants, and to punish such crimes by hounding culprits relentlessly. The Erinyes are crones and, depending upon authors, described as having snakes for hair, dog's heads, coal black bodies, bat's wings, and blood-shot eyes. When they are angered their skin is said to turn charcoal black, but when appeased it becomes white. In their hands they carry brass-studded scourges, and their victims die in torment.
While there are various accounts that detail their creation, their exact origin is unknown. However, the more widely known version is that they were created when Cronus castrated his father Ouranos, and threw his genitalia into the sea. From his drops of blood, the Erinyes were born. They were later placed in Hell, and were tasked with punishing those who committed ill will towards others. Despite being residents in the Inferno, they are not bound by other demon lords such as Satan, as such the king of Hell has no control over them. However, should a damned soul attempt to escape or if a human committed atrocities that fit the description of which they oppose, the Devil can send the Erinyes to perform their sworn duty.
The three well known Erinyes were Alecto ("unceasing"), Megaera ("grudging"). and Tisiphone ("vengeful destruction"). Alecto was charged with punishing those who committed moral crimes as anger, especially when used against others, and was the goddess of Anger. Megaera was the goddess of Jealousy; she punished those who had committed crimes such as cheating and adultery. Tisiphone was the third sister and the goddess of Vengeance, punishing those who have committed the crimes of murder: patricide (killing leaders or your father), fratricide (killing your brother) and homicide.