The Age of the Spirit was the pinnacle of ancient humanity's civilization and technological development.
Their battles were not fought with fists, feet, and clashing blades. Instead, they cultivated and absorbed the spirits of various beings from the Yin Realm, using demonic spirit arts to conjure illusory phantoms of demonic beasts and monstrous birds. Their spirit techniques and demonic arts were like spells that could summon armies from thin air. When the two sides clashed, all one could see were terrifying, apocalyptic phantoms.
