The Zerg Swarm is a race of xenomorphic "hyper-evolutionary" superorganisms. Unlike the Protoss and the Terrans, the Zerg are not "tool-makers", lacking technological inclination; instead, they "force-evolve" genetic traits by directed mutation in order to match such technology. Operating as a hive mind-linked 'chain of command', the Zerg strive for genetic perfection by assimilating the unique genetic adaptations of "worthy" races into their own, creating numerous different strains of Zerg.

The savage Gashyrr Wasps of Eldersthine were initially inducted into the Swarm to serve as resource gatherers. Over time they became Drones, engineered with the Larvae’s ability to break down their own genetic code. Like Larvae, Drones are controlled by the Overlords, who monitor their progress through a type of instinctive telepathy. Drones are single-minded about their tasks, diligently working even in the face of raging combat and the possible destruction of the Hive.