The Mezlag sector was a major power in its niche of space in the Unknown Regions, the home of the Mezlagob system and the eponymous Tetrarchy of Mezlagob. It included all four of the founding worlds of the Tetrachy (Mezlagob, Ommol, Hudrel, and Telacia), as well as roughly two dozen of its other worlds. The Keblygrin Way passed through the Mezlag sector, as did the Liberators' Run.
During the Great Liberation, the Mezlag sector held out the longest against the Golden Empire, falling only once the Xoquon sector had successfully revolted against its rule and the Empire had captured the Vall`to sector. In 102 ABY, Ommol fell and the Tetrarchy became extinct. The Golden Empire continued to administer the Mezlag sector, extending its borders to encompass some nearby systems which the Tetrarchy had either not discovered or not conquered successfully.