The Harpe was born at the very beginning of the Greek cosmos, in the first act of violence that shaped the world. Gaia, the earth, had given birth to Uranus, the sky, and together they had produced the Titans, the Cyclopes, and the Hecatoncheires, the hundred-handed giants. But Uranus hated his children and hid them inside Gaia's own body, causing her terrible pain. Gaia fashioned a sickle of grey adamant, the hardest substance in existence, and gave it to her youngest and bravest son, the Titan Cronus. Cronus lay in wait for his father and, when Uranus came down to lie with Gaia, struck him with the harpe and castrated him, casting the severed parts into the sea. From the blood that fell upon the earth sprang the Furies, the Erinyes, the goddesses of vengeance who pursue oath-breakers and kin-slayers to the ends of the world. From the foam that gathered where the parts fell into the sea rose Aphrodite, the goddess of love and beauty. The harpe had changed the cosmos with a single stroke, dethroning the sky and setting in motion the age of the Titans.

The blade passed from Cronus to Zeus, or so some accounts suggest, for the king of the gods was said to have used it against Typhon, the vast serpentine giant with a hundred dragon heads whom Gaia sent to overthrow Olympus. But the harpe's most famous bearer was not a god but a mortal hero, a young man named Perseus, the son of Zeus and the princess Danae of Argos. Danae's father, King Acrisius, had locked her in a bronze tower because an oracle had warned him that her son would one day kill him, but Zeus visited her in a shower of gold and Perseus was born. Acrisius cast mother and child into the sea in a wooden chest, and they washed up on the island of Seriphos, where the fisherman Dictys raised the boy. When Perseus grew to manhood, the king of Seriphos, Polydectes, desired Danae and sent Perseus on a quest he believed would kill him: to fetch the head of the Gorgon Medusa.

The Gorgons were three sisters, daughters of the sea gods Phorcys and Ceto, and they lived at the western edge of the world, beyond the known lands, in a place where the sun set into the ocean. Stheno and Euryale were immortal, but Medusa had once been a beautiful maiden who had lain with Poseidon, the god of the sea, in a temple of Athena, the goddess of wisdom and war. Athena, enraged by the desecration of her shrine, had transformed Medusa's lovely hair into a nest of venomous serpents and made her face so terrible that one look turned living things to stone. Medusa was the only mortal of the three, and that mortality was her weakness.

Perseus could not face the Gorgons alone, and the gods came to his aid. Athena, perhaps seeking to undo some of the harm her curse had caused, gave him a polished bronze shield to use as a mirror, so that he could see Medusa's reflection without looking directly at her face. Hermes, the messenger god whose winged sandals carried him across the world in hours, gave him the harpe, the curved blade of adamant that had once castrated Uranus and that no mortal smith could forge. Some say Hermes gave it from his own hand; others say the nymphs who guarded the treasures of the gods provided it, along with the winged sandals, the cap of invisibility, and a leather bag to carry the severed head. However it came to him, Perseus took the harpe and felt its weight, the curve of its edge, the balance that spoke of divine craft.

He flew west on his winged sandals, invisible in the cap of Hades, and found the Gorgons sleeping in their cave, the serpents of Medusa's hair hissing and coiling in their dreams. He approached with the shield held before him like a mirror, watching Medusa's reflection, and when he stood over her he raised the harpe high and brought it down in a single sweeping stroke. The blade cut through the serpent locks and the immortal flesh beneath, and Medusa's head fell from her body. From the stump of her neck sprang two beings: Pegasus, the winged horse who would one day carry the hero Bellerophon to slay the Chimera, and Chrysaor, the warrior with the golden sword who would father the three-headed giant Geryon. Perseus snatched up the head by its snaky hair, dropped it into his leather bag, and fled before Stheno and Euryale could wake and pursue him.

The harpe appears again in the story of Perseus's return. He flew over Libya, and drops of blood from the Gorgon's head fell upon the sand and turned into venomous serpents that have infested the desert ever since. He came to the land of the Aethiopians, where the princess Andromeda was chained to a rock as a sacrifice to a sea monster sent by Poseidon, and he used the harpe to kill the beast and claim her as his bride. He returned to Seriphos and found Polydectes threatening his mother, and he pulled the Gorgon's head from the bag and turned the king and his court to stone. Then he gave the head to Athena, who fixed it upon her shield, the aegis, where it would turn her enemies to terror forever.

What became of the harpe itself, the old stories do not say with certainty. Some say Perseus returned it to Hermes, who had lent it as a god lends to a mortal, expecting it back. Others say he kept it as a heirloom, the blade that had made him a hero, and that it passed to his descendants, the kings of Mycenae, and from them into legend. The curved blade became the model for the sickle-swords of the ancient near east, the harpe that reapers carried at harvest and that the figure of Time, old Cronus himself, still wields in Renaissance art. From the castration of Uranus to the beheading of Medusa, from the forge of the Titans to the hand of a mortal hero, the harpe remains the blade that cuts what cannot be cut and changes what cannot be changed.