The Furies, also known as the Erinyes are monsters of Vengeance who serve the god Hades. They are his torturers in the Underworld and punish the crimes of the wicked. In Greek mythology, each Fury was sometimes represented as avenging a certain type of crime, such as crime, grudges, or murder. Ironically enough, they are often referred to as the Kindly Ones, in order to remain safe from them. They are sometimes misidentified with the arai, spirits of curses. Their Roman counterpart are the Dirae.
After Kronos' defeat in the Titanomachy, his three powerful sons would divide the world between themselves, with the eldest, Hades, receiving the Underworld, and hired the Furies to help him enforce his authority and justice among the numerous souls of the dead that entered his infernal realm. They would be in charge of monitoring the Fields of Punishment, and would sometimes be dispatched by Hades to bring living sinners to justice as well, ruthlessly torturing them into insanity unless they made amends for their grievous sins. As a results, mortals would come to fear the Furies so much, that they would take to referring to them with various euphemisms, such as "The Kindly Ones".
The famous demigod musician Orpheus, devastated by the untimely death of his wife Eurydice, creates a new entrance to the Underworld with his beautiful music and singing. He made his way all the way to Hades' palace, with ghosts, monsters, Charon, Cerberus, and even the Furies themselves being brought to tears by his ineffably lachrymose and beautiful music. Theseus was also affected by the Furies. When he and one of his good friends decided to kidnap Persephone, they went into the underworld destroying monsters and scaring ghosts. They also intimidated Charon to take them across River Styx. Finally, when they were almost at Hades's palace, they decided to take a rest. When Theseus woke up, he was paralysed and his friend has turned into stone and crumbled. The Furies hover on top of them, saying it is a rightful punishment for trying to kidnap Persephone. Theseus is freed after Hercules went into the underworld to capture Cerberus.
Alecto is disguised as Mrs. Dodds: a pre-algebra teacher at Yancy Academy. She dislikes Percy Jackson and always seems to prefer Nancy Bobofit, the class bully. It is later discovered that she was actually one of the Furies and thus not a human. On a field trip to the Metropolitan Museum of Art, Percy kills her with Riptide (Although he does not realize it is Riptide yet; he thinks that he hallucinated everything that happened, including Mr. Brunner throwing him the pen.) and the monster disintegrates into dust.
Percy encounters the Furies when in the Underworld upon encountering Hades. After hearing what really occurred with the theft of Zeus' master bolt and Hades' helm of darkness during Percy's fight with Ares, the Furies arrive once the battle has ended, and Percy gives them the Helm to return to Hades.
It is revealed that Alecto was the "lawyer" who brought Nico and Bianca di Angelo to the Lotus Hotel and Casino under Hades's orders. After about 70 years, Hades had the Fury get his children out as he hoped that one of them could be the child in the Great Prophecy. The Furies also appeared to carry Nico and Percy to Hades's throne room before Percy bathes in the River Styx.
When Percy and Annabeth were attacked by the arai, Percy initially thought that they were the Furies. Then he noted that there were several arai, contrary to only the three Furies, and none of them have whips. Later, he noted that the Furies were better, as they could at least be contained by Hades.
As seen in The Lightning Thief the Furies have leathery wings like bats, claws, a mouth full of huge yellow fangs, and glowing eyes. They carry whips that dance with flames every time they flick them. While disguised as mortal women, they carried handbags, wore crumpled velvet dresses, and shapeless knit hats of different colors.
Furies are extremely powerful, as the lieutenants of Hades. They can change their appearance at will into human forms, regardless of gender. They also possess superhuman strength and speed, exponentially surpassing that of a human being. Because of their wings, they are capable of flight, and wield powerful whips that induce immense pain on contact and are possibly pyrokinetic. The full extent of their powers is unknown, but since Hades entrusted them with hunting down Thalia at Half-Blood Hill, and to generally pin down and relentlessly torment sinners until they either repented or regretted their mistakes, they obviously possess other, unseen powers that are formidable in their own rights.
- Alecto seems to be the leader of the three because she is always in the middle and Hades always makes her do the work.
- According to Percy Jackson's Greek Gods, the Furies rose from droplets of Ouranos' blood, which had splattered everywhere when Kronos killed Ouranos. However, in The House of Hades, it is Nyx who claims to be their mother.
- In the story of Canto VIII of Dante's Inferno they confront the poets Dante and Virgil at the gates of the city of Dis. The heads of the Erinyes, whom the two poets met in Canto IV, were wreathed with serpents and their eyes dripped with blood, rendering their appearance rather horrific.
- Their Egyptian equivalent is Shezmu.
- Their Norse equivalent, in terms of attribute, is Nerthus.
- In some stories the Erinyes are said to be children of Hades, and in some they are children of Nyx.