This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Echidna (Greek)
Echidna was half beautiful maiden and half fearsome snake. Hesiod described "the goddess fierce Echidna" as a flesh eating "monster, irresistible", who was like neither "mortal men" nor "the undying gods", but was "half a nymph with glancing eyes and fair cheeks, and half again a huge snake, great and awful, with speckled skin", who "dies not nor grows old all her days".
Aristophanes (late 5th century BC), who makes her a denizen of the underworld, gives Echidna a hundred heads (presumably snake heads), matching the hundred snake heads Hesiod says her mate Typhon had. In the Orphic account (mentioned above), Echidna is described as having the head of a beautiful woman with long hair and a serpent's body from the neck down.