The story of Scylla begins with the story of Glaucus. Glaucus, once a fisherman, tasted some enchanted grass near the sea, and immediately was possessed to jump in the water. The sea gods Ocean and Tethys received him and made him immortal, as they were. When the transformation was complete, Glaucus was a sea-god with with sea green hair and a fish tail. This form appeared strange to land-dwellers, and so it was with Scylla. Scylla was a beautiful nymph who Glacus had his eye on. Unfortunantly, Scylla would have nothing to do with Glaucus and ran away.

To solve this problem, Glaucus went to Circe (the witch goddess). He begged her for a love potion to make Scylla desire him as much as he desired her. While they became acquainted, Circe fell in love with Glaucus. After refusal of anyone but Scylla, Circe became mad... Not at Glaucus, but at Scylla. Circe prepared a potion that she dropped into the bay Scylla bathed in. When Scylla entered the water, she changed into a monster with serpents and dog heads coming out of her body. She was also rooted to a rock at the bottom of the ocean to wallow in her misery and to take it out on sailing travelers (such as Aeneas, Jason, and Odysseus).