Soon after this, the Terrans discover that a second alien race, the insectoid Zerg, has been stealthily infesting the surface of several of the Terran colonies, and that the Protoss are destroying the planets to prevent the Zerg from spreading.
Pouco tempo despois os Terran descobren que unha segunda especie alieníxena, os insectoides Zerg, estivera infestando de forma encuberta a superficie de varias das colonias Terran, e que os Protoss están a destruír estes planetas para previr o avance dos Zerg.