In the world, there were gods who obeyed the rules, whether good or evil. But there were also evil gods who defied the rules. When a traverser was confronted by the rules that he could never conform to, the resulting collision marks the beginning of the story of an evil god… This is the story of a good man who transformed into a great jellyfish, then traversed his world to arrive at a world of swords and magic. His journey of searching and exploring eventually led to him remaking nature and changing the world.
Satan coming out of seclusion was indeed because he'd already cultivated himself to the peak of the Legendary Realm.
In theory, the Legendary Realm was without limits; even if there was no way to become a demigod, you could still grow stronger at an unceasing pace, continuously becoming more and more powerful.
Such Legendary Masters had existed back in relatively more savage, ancient times. Their formidable level was such that it was even enough to shock the gods—forget weak Divine Power, even if you had low-level Divine Powers, it wouldn't necessarily be enough to compete with them.
But legendary was still legendary. If you hadn't truly completed your life's transformation, that meant you hadn't escaped the river of time and had ignored the ability available to you as it passed you by. Following the passage of time, these impossibly powerful Legendary Masters were ultimately unable to defeat time itself, each of them growing older and dying instead.