The xel'naga discovered the volatile ash-world of Zerus while searching for a counterpart to the protoss to perpetuate their life cycle. The xel'naga raised the zerg from one of the world's insignificant lifeforms.Having matured under the Overmind, the Zerg Swarm attacked the xel'naga worldships in orbit. The Swarm absorbed some of the xel'naga's knowledge, and then left Zerus in search of the protoss. They left a burning and lifeless world. The few primal zerg that remained inherited the planet and thrived.
Over the millennia, Zerus became verdant with large swaths of jungle and areas of volcanic activity.
Zeratul visited Zerus. During the Second Great War, he convinced Sarah Kerrigan to journey to Zerus and claim the primal zerg's power. Kerrigan used the first spawning pool to morph back into a human-zerg hybrid, this time free of Amon's influence, and killed Zurvan, along with the other resisting pack leaders, and absorbed their essence. The Swarm departed with Dehaka and allied primal zerg whom followed Kerrigan for more essence.
