Nemean Dragon was a creature born from Gaia in the mythology of Ancient Greece.
The Nemean Dragon was larger than average dragon in Greek mythology. It had poisonous fangs and three rows of teeth as well as three-forked tongue. It guarded sacred grove of Zeus in Nemea. However, during drought that had been caused by Dionysus, the dragon had become restless from thirst and it's actions were unpredictable. In this aggravated state it killed an infant prince Opheltes by accident in it's search for water. As a consequence the dragon was slain by seven armies that had gathered nearby with a spear thrown by a renowned warrior named Capaneus.
Zeus was angry when he lost his guardian, and was about to strike Capaneus dead with a lightning bolt. However, he decided to wait for the worst possible moment to have his revenge. Zeus fulfilled his plan in a pivotal battle in which the army took part.