The Dirae are also known as the Furies or the Erinyes. They're the three daughters of Uranus and Gaia – Megaera, Alecto and Tisiphone. The furies are the bat-winged spirits of vengeance and they guard the gates of Dis, the city of the Underworld. As well as administering punishment to those in Level Six in Hell, they take new souls down to the lower levels when they're delivered to the gates of Dis.
These three are so implacable in their fury that most called them the Eumenides (soothed ones) or Semnai Theai (honourable goddesses) so as not to incur their wrath.
“William-Adolphe Bouguereau (1825-1905) – The Remorse of Orestes (1862)” by William-Adolphe Bouguereau – Unknown. Licensed under Public domain via Wikimedia Commons.
Megaera
Megaera's name means grudging or jealous rage. She not only works in Hell, but occasionally mans the reception desk for the HELL Corporation. She was the receptionist on the day of Mel's interview and grudged the angel everything from information to common politeness to a smile.
Alecto
Alecto's name means endless or unceasing in anger.
Tisiphone
Tisiphone's name means punishment, vengeful destruction or avenger of murder.