A collection of Dark Side empowered femtotech entities that can exhibit collective consciousness. They are known to have destroyed a moon in the Corellian system, ultimate reasons unknown. This led to the evacuation of the Republic govenrment from Corellia. They can also "take over" sentients by infiltrating their bodies, either to extract intelligence and/or to establish control and impersonate people. Certain powers such as Dark Side Dissipation and Force Harmony have been known to limit their effectiveness, but they do not seem bound by the laws of physics, let alone the Force. Some super-weapons developed through the Exordium project and others designed by Aenea have limited effectiveness until they learn how to neutralize them. Conventional weapons are utterly ineffective.

It has been suggested by Davrosh that they are a creation or discovery of Darth Laut that is now potentially beyond his control. If that is true, civilization and possibly sentient life itself may be at risk of extinction in the Known Galaxy.

As of the beginning of the New Game, much of the coreward "old quadrant" of the galaxy (that defined by the Perlemian Trade Run and the Hydian Way) has been destroyed, along with many additional systems. Between this and the Sith attack, there is very little left of the Galactic Republic that was not backwater just a few years ago. The Jedi Order, Sith, and Tion Principality forces have declared a truce and are working together to exterminate the swarm, although with its geometric growth rates, it may be an impossible task. That the groups are fighting the swarm does suggest that there are super-weapons not adaptable to by the swarm or some other set of secret weapons that can be deployed against it.