The zerg are a race entirely unlike the terrans or the protoss. They are composed of many different species integrated into the Swarm via zerg infestation. These creatures are rapidly and selectively evolved into deadly and efficient killers to further the driving zerg imperative of achieving absolute domination. The zerg make no use of technology to create their weapons, armor, or starships. Instead, these functions are efficiently fulfilled through biological adaptation and planned mutation of the zerg strains. Even zerg buildings are in fact specialized organs within the living, growing organism of a zerg nest.
When the zerg first arrived in the Koprulu sector, they were unified by their absolute obedience to the zerg collective sentience known as the Overmind. The Overmind ultimately directed the actions of every zerg creature in the Swarm, functioning through a hierarchy of lesser sentiences. The first and most important tier of these consisted of the cerebrates, each entrusted with direct control of a sizable section of the Swarm. The cerebrates' commands were disseminated in turn by the overlords, which directly ordered and controlled the mass of zerg creatures both in their nests and on the battlefield.
Although the Overmind was primarily driven by its desire to consume and assimilate the advanced protoss race, it found useful but undeveloped material in humanity. Taking a powerful terran psionic, Sarah Kerrigan, the Overmind evolved a new and unique creature: the Queen of Blades. When the protoss destroyed the Overmind during the invasion of Aiur, the Queen of Blades manipulated the dark templar into eliminating the surviving cerebrates. As a result, she came to dominate the Swarm.
虽然overmind的根本目的是要毁灭先进的protoss并吸收他们的基因为己有，它在人类身上发现了十分有用但未开发的东西。在感染了一个强大的terran psionic（具有幽能的terran，幽能是ghost的特殊能力），Sarah Kerrigan之后，overmind进化出了一个新的并且是唯一的生物：the Queen of Blades（刀锋女王）。当overmind在入侵Aiur中被protoss摧毁后，刀锋女王操纵黑暗圣堂消灭了其余活着的cerebrates，并最终统治了虫群。