The Moirai(The Fates) were the three goddesses of destiny in Greek mythology. They were Clotho, Lachesis and Atropos(Greek: Άτροπος).
They controlled the life and destiny of everyone. Clotho spins the thread of life (begins a person's or creature's life), Lachesis measures it (looks at the how long it currently is), and Atropos cuts the thread. When the thread is cut the person dies. The Moirai are capable of destroying an immortal.
The decisions of the Moriae about a person's life cannot be changed. Even Zeus is powerless to change their will.
The parents of the Moirai are not surely known. Some said they were the daughters of Zeus and the Titaness Themis, or more likely of primordial beings like Nyx, Chaos or Ananke.
Their Roman equivalent were the Parcae.
Sources: D'Aulaire's book of Greek Myths
Images for kids
An 1886 bas-relief figure of Dike Astraea in the Old Supreme Court Chamber at the Vermont State House.
Bas relief of Lachesis. Base of a lampstand in front of the Supreme Court of the United States Washington, D.C..
Bas relief of Clotho. Base of a lampstand in front of the Supreme Court of the United States, Washington
Macbeth and Banquo meeting the three weird sisters in a woodcut from Holinshed's Chronicles.