Serpent

The Greeks and Romans considered the serpent as symbolical of guardian spirits, and as such were often engraved on their altars. See Aesculapius, Apollo, Chimaera, Eurydice, and Medusa. “Pleasing was his shape, And lovely; never since of serpent kind, Lovelier; not those that in Illyria changed Hermione and Cadmus, or the god In Epidaurus, nor to which transformed Ammonian Jove, or Capitoline, was seen.” Milton.