 He also assimilated Sarah Kerrigan so as to create a weapon to free the Zerg from the control of his Dark Master.The Zerg and Protoss clash on various Terran worlds, eventually leading to Zeratul assassinating the cerebrate Zasz.Zasz's death momentarily links the minds of the Overmind and Zeratul, allowing the Overmind to learn the location of the Protoss homeworld Aiur.