Sygma is an ancient but advanced civilization located somewhere in the Pacific Ocean that predated even the Mycenae Empire. It is also where the inhabitants of Planet Fleed and the Vegan Empire originated from. It was only featured in the Grendizer manga by Gosaku Ōta.
Sygma was a peaceful kingdom for many generations. However, at some point two sides of the empire eventually broke out in battle that went on for many years and they eventually took their battle to outer space where the warring sides took up residence on the planets they named Fleed and Vega. After which, very few people remained on Sygma and many of them eventually died out with the empire lost to history. However, their technology and influence had remained with Planet Fleed creating the Grendizer based on the Sygma ship Great Spirit Raaga, the early Mycenae Empire worshipped Raaga as a god, and even a city a distance from the Mycenae capital continued to thrive until Duke destroyed it. Sayaka Yumi during a battle between Grendizer, the Vegan Empire, and Earth's governments was transported through a ring from the empire. The last king of Sygma, Zeus told Sayaka Sygma's story and showed her how to use the ring to pilot Raaga. With Sayaka now his successor, Zeus died peacefully bringing an end to Sygma.