Two Hegemon-Level Civilizations
A hegemon-level civilization was one that had once possessed the ability to dominate the galaxy. In this galaxy, the Rakatans of the Infinite Empire counted as one, while the humans of the Galactic Republic and Galactic Empire could barely count as another. As for the Fourth Civilization, it had two.
The Protoss and the Vasari.
Both races had once dominated the galaxies they inhabited. The Vasari had gone even further, bringing their entire galaxy under their control.
For that very reason, both the Protoss and the Vasari far surpassed other races in terms of technological level and racial traits.
With their telepathy, psionic gifts, and physical abilities, the Protoss could almost be called a perfect race. The Vasari, meanwhile, had gained complete control over their own genes, allowing them to adapt to all manner of environments and roles.
Technologically, they stood generations ahead of every other civilization in the current galaxy.
Incidentally, super-races like the Kilik Swarm, which had not only controlled an entire galaxy but also had countless ties to the Celestials who had once created it—and might even have participated in the possible "Twilight of the Gods" a hundred thousand years ago—should sit at the same table as beings like the Protoss and the Precursors. They belonged to the category of ancient super-civilizations.
Those were not under consideration. After all, for such super-civilizations, ruling the galaxy they inhabited was merely a basic requirement. Their true pursuit was to reach a higher realm, whether by escaping their current dimension or breaking free of the shackles of flesh.
Of course, the mothership's database and cryogenic chambers also contained beings such as the Forerunners and the Ploo people. They could likewise be considered hegemon-level races. Tang Xiao simply had no intention of awakening them for the time being.