And in a hollow cave she bare another monster, irresistible, in no wise like either to mortal men or to the undying gods, even the goddess fierce Echidna who is half a nymph with glancing eyes and fair cheeks, and half again a huge snake, great and awful, with speckled skin, eating raw flesh beneath the secret parts of the holy earth. And there she has a cave deep down under a hollow rock far from the deathless gods and mortal men. There, then, did the gods appoint her a glorious house to dwell in: and she keeps guard in Arima beneath the earth, grim Echidna, a nymph who dies not nor grows old all her days.
Men say that Typhaon the terrible, outrageous and lawless, was joined in love to her, the maid with glancing eyes. So she conceived and brought forth fierce offspring; first she bare Orthus the hound of Geryones, and then again she bare a second, a monster not to be overcome and that may not be described, Cerberus who eats raw flesh, the brazen-voiced hound of Hades, fifty-headed, relentless and strong. And again she bore a third, the evil-minded Hydra of Lerna, whom the goddess, white-armed Hera nourished, being angry beyond measure with the mighty Heracles.
- Hesiod, Theogony