Echidna is a Greek monster depicted as being half snake, half woman. Her parentage is debatable, but it is most often stated that she was the daughter of either Gaia and Tartarus, or of the sea monsters Phorcys and Ceto. The wife of Typhon, she is the mother of a large number of the monsters of Greek myth. Her many children include the Chimera, Cerberus, Orthrus, the Hydra, the Sphinx and the Nemean Lion. She was eventually slain by Hera's servant, the hundred-eyed giant, Argus.
"Origin: Greece. The mother of all monsters. Her upper half is a beautiful woman, and her lower half is a spotted snake. Her offspring include such beasts as Orthrus, Cerberus, Hydra, Chimera, and Ladon."
—Shin Megami Tensei A-Mode DDS dictionary
In the GBA/iOS versions, if Pascal-Cerberus's mind is restored with the Golden Apple at the entrance to Tokyo Destinyland, the protagonist will receive the Dog Collar Visionary Item upon Echidna's defeat.