From the introduction: The zerg swarm is a race of biological advanced aliens. They are monstrous in appearance, and encompass a wide variety of species are genetically engineered to be the perfect tools for the swarm’s prevalence. The zerg actively assimilate other races into their swarm, mutating them into new strains or taking worthwhile traits that are of interest to the leaders of the swarm. Relentlessly, the zerg crusade across the Koprulu sector spreading colonies to all worlds, occupied or unoccupied. Their purpose is simple: eradicate and evolve.