Furies (mythology) or Fury (mythology), per precedent.
Talk about it here.
Madame Kovarian told Melody Pond, Brooke, H-One, H-Two, and O terrifying bedtime stories about them when they were children. According to Kovarian's version of the legend, the Furies had powers to rectify any problem in the world by laying a grievance at their feet and punishing a guilty person to death. Kovarian believed the legend was a good foundation to teach Melody about why she needed to kill the Doctor. (AUDIO: The Furies)