Taking a more supernatural approach, I'd like to imagine the new faction as some sort of remnant of an ancient race. I picked the name, Requiem, for several reasons.

First of all, there is the association with souls and the dead. The name is also shortened from Requiem Mass, a gathering of people of indefinite shape and considerable size meant to put the dead to rest.

Another reason is a requiem's purpose of repose, calmness, and tranquility.

Maybe the race seeks a salvation of sorts or a peaceful end to their unnatural existence. Maybe they were disturbed from a tranquil slumber and wish to return to their rest by "silencing" the rest of the galaxy. While I don't want to shoehorn the direction of the faction's setting through the name, I feel that there's potential in the connotations of a requiem.

Aside from possible lore directions, the aspect of tranquility and calmness could also associate with the "espionage" or "stealth" components of the faction.