The Lernaean Hydra is so far our favourite creature in all classical mythology.
The Hydra was a gigantic creature, like a serpent with multiple heads, when one the head was chopped off, two or three heads grew up from that- the symbology and the metaphor is very interesting and i can see this as model of life. To kill the Hydra was one of the twelve labours of Hercules, that was the story that introduced me to this fantastic creature.