The Evergreen Immortal Empire was different from the Eastern Sage Immortal Sect. The Evergreen Immortal Empire was the official name for the nation, while the Eastern Sage Immortal Sect used the structure of a sect to govern the Eastern Sage Thirteen Prefectures. Hence, the people of authority had different titles.
The position of the Everpeace Marquis was equivalent to a prefecture lord in the Eastern Sage Thirteen Prefectures. He controlled a large area and his authority towered up the sky. He was also an immortal king, and it went without saying that he was an exceptionally powerful one.