Thousands of years ago, after the war between the Titans and Olympians, Gaea was enraged at the defeat of the Titans (her children), and of how they were locked away in Tartarus. She attempted revenge by sending her last and most powerful child, the great monster Typhon to destroy the gods. Typhon alone is the greatest foe the gods ever faced, even mightier than the Titans themselves.
Having never anticipated such a rival, the gods were quickly forced on the defensive and they eventually went into hiding. Athena, however, stood her ground and convinced Zeus to fight by calling him a coward. This convinced Zeus and he went into battle with his lightning. Zeus struck Typhon square in the chest with lightning at point blank range, greatly weakening him. The gods were then able to trap him under Mount Etna, where his raw power itself causes lava to ignite from the mountain top in the form of a volcano. After the defeat of her most powerful child, Gaea admitted defeat and fell back to sleep, allowing the gods to rule Olympus without interference.