C1018 Boundary seal upgrade

There were only four cities with a population of a hundred million in the entire God Realm. They were the main cities of the Four Great Heavenly Domain. And the only main city in the sky that was the location of Liuyan Pavilion was the Demon Sound City, the headquarters of Magic Sound Sect. Thus, the Ling Yan City which was controlled by Liuyan Pavilion was already pretty good