“Vain and foolish girl,” Athena said angrily, “You think you are prettier than I am! I doubt it to be true, but even if it were -- there is more to life than beauty alone. While others work and play and learn, you do little but boast and admire yourself.”
Medusa tried to point out that her beauty was an inspiration to those around her and that she made their lives better by simply looking so lovely, but Athena silenced her with a frustrated wave.
“Nonsense,” Athena retorted, “Beauty fades swiftly in all mortals. It does not comfort the sick, teach the unskilled or feed the hungry. And by my powers, your loveliness shall be stripped away completely. Your fate shall serve as a reminder to others to control their pride.”
And with those words Medusa’s face changed to that of a hideous monster. Her hair twisted and thickened into horrible snakes that hissed and fought each other atop her head.
“Medusa, for your pride this has been done. Your face is now so terrible to behold that the mere sight of it will turn a man to stone,” proclaimed the goddess, “Even you, Medusa, should you seek your reflection, shall turn to rock the instant you see your face.”
And with that, Athena sent Medusa with her hair of snakes to live with the blind monsters -- the gorgon sisters -- at the ends of the earth, so that no innocents would be accidentally turned to stone at the sight of her.