The Yor are a race of self-replicating machines created by the Iconians to serve the Precursors. A malfunction had caused them to revolt against their creators and destroy them. Afterward, they had banded together to form the Yor Collective, and they are now one of the most insidious races in the galaxy, surpassed only by the Drengin and, of course, the Dread Lords.
The Yor are machines built from advanced Precursor technologies. Being machines, it is easy to believe that there are many different configurations of Yor for specific roles, from basic worker drone to supreme leader (though there has not been any Yor leader besides N-1 to the best of our knowledge). Despite being machines, by technological standards, they rely on an organic fuel source, or food in layman's terms, and have not reconfigured to rely on indefinite power sources, like fusion power.
It has been observed that Yor civilians do indeed have some semblance of free will, despite their dystopian society, and have developed a culture that can be integrated into the galactic community (though it is difficult to distinguish their culture from propaganda). The fact that the Yor are utterly loyal to their collective allows them to virtually resist cultural influnce and prevent colonies from defecting to other empires.
The Yor's most infamous aspect is their ultimate goal to exterminate all organic life in favor of cybernetic organisms, like themselves. Their mindset makes them very dangerous and difficult to negotiate with, however they had no qualms about allying with the Drengin Empire, as they had shared a common goal (galactic domination) and the alliance would help the Yor further their master plan, since the two empires possessed superior militaries.
The Dark Yor
Recently, a small faction of sentient war machines calling themselves the "Dark Yor" have made themselves known to the galactic community. They do share some characteristics of the Yor, but it is uncertain if they are truly related. It is easy to believe that the Yor don't take kindly to the fledgling race.