The Graes were three sisters who lived in the Western extreme of the ocean. Their names were Deino, Pephredo, and Enyo, which mean "alarm," "dread," and "horror." They were the daughters of Phorkys and Keto. The belief in their existence seems to have been originally suggested by the gray fog or mist which lies upon the sea and is a frequent source of danger to the mariner.
They look like old ladies, born old, with long gray hair, and shaped like swans. Other tales pretend that the Graes shared one eye and one tooth among one another and were believed to be hideous looking creatures.
They dwelt near the entrance to the Underworld, and were the guardians of the Gorgons. They protected the nymphs, who protected Hades' invisible helmet and a pair of winged sandals belonging to Hermes. They also oversaw the safety of the shield of Athena.
One of the most famous known encounters with the Graes is the story of Perseus. Perseus snatched the Graea's only eye and said that he would not return the eye until they told him where the Gorgon's lived. In desperation the Graea told Perseus where they lived, which further led him to finding Hades invisible helmet and winged shoes. From there Perseus was able to destroy Medusa because of his invisibility and his ability to fly.