The Chaos Emeralds arrival on Mobius happened roughly 11,950 years ago, during the Saurian Age in which Mobosaurs dominated the planet. Mysteriously, the sky turned green and the green colored Chaos Emeralds rained down on the planet. This resulted in bizare weather changes which wiped out the Mobosaurs. However, three Mobosaurs, later known as the Ancient Walkers, managed to survive, having obtained Chaos Emeralds during their arrival on the planet and gained god-like powers, wisdom and insight from the emeralds. (StH: #148, TMS: #3)