Scylla , in Greek mythology. 1 Sea monster. According to one legend Circe, jealous of the sea god Glaucus' love for Scylla, changed her from a beautiful nymph into a horrible doglike creature with six heads and twelve feet; according to another, Amphitrite, jealous of Poseidon's love for her, transformed her into the ugly monster. Scylla lived on the rocks on the Italian side of the Strait of Messina, where she seized sailors from passing ships and devoured them. On the other side of the strait was the whirlpool Charybdis. Odysseus in his wanderings passed between them, as did Jason and the Argonauts. 2 Daughter of Nisus, king of Megara. She betrayed her father to his enemy Minos, but when she sought Minos' love, he scorned her.