The Great Demon Capital City was the former headquarters of the Ancient Demon Sect.
After the Ancient Demon Sect was defeated by the Ancient Profound Celestial Sect, its experts each fled the Great Demon Capital City, taking their legacy Celestial Steles with them.
Murong Hai, the founding ancestor of the Great Zhou Demon Country, was a peerless expert who had obtained the legacy of the Ancient Demon Sect. After bursting onto the scene, he united with many other experts who had also inherited the Ancient Demon Sect's legacy, and together they defeated the Ancient Profound Celestial Sect, which had been crippled in its war with the Ancient Demon Sect.
After the Ancient Profound Celestial Sect withdrew from the region, Murong Hai, the founding ancestor of the Great Zhou Demon Country, established the Great Zhou Demon Country in the Great Demon Capital City and decreed a state policy: the Great Zhou Demon Country would share dominion over the realm with the various Demon Sects.
