Hidden Empire is the first book in The Saga of Seven Suns series by Kevin J. Anderson, published on July 24, 2002.
Having colonized many worlds in the Spiral Arm, humanity is divided into three branches: the Earth-based Terran Hanseatic League (Hansa) and its subordinate planets, the independent world Theroc with its telepathic green priests, and the Roamers, interplanetary traders who prefer starships and hidden bases to a conventional planet-based civilization.