Moirai

In Greek mythology, the Moirae or Moirai (also called the Three Fates) were the personifications of destiny. They controlled the fate of every mortal and immortal from birth to death (and beyond). Even the gods feared the Moirae. They were the daughters of Zeus with either Ananke or, more frequently, Themis.

The three Moirae were Clotho, Lachesis and Atropos. They controlled the metaphorical thread of life for every person.

Clotho ("spinner") spun the string of life with her distaff.
Lachesis ("alotter" or drawer of lots) measured the thread of life, thereby determining how long people, animals and deities existed.
Atropos ("inflexible") was the cutter of the string of life. She chose the manner of a person's death. When she cut string with "her abhorred shears", someone on earth died.

The Moirae were usually described as cold and unfeeling, and depicted as old crones or hags.

After Admetus' thread was cut, Apollo intervened with the Moirae, who agreed to let Admetus live if someone else took his place. His wife, Alcestis agreed and died but was rescued from the underworld by Heracles.