Blizzard Entertainment's bestselling real-time strategy game series StarCraft revolves around interstellar affairs in a distant sector of the galaxy, with three species and multiple factions all vying for supremacy in the sector. The playable species of StarCraft include the Terrans, humans exiled from Earth who excel at adapting to any situation; the Zerg, a race of insectoids obsessed with assimilating other races in pursuit of genetic perfection; and the Protoss, a humanoid species with advanced technology and psionic abilities, attempting to preserve their civilization and strict philosophical way of living from the Zerg. Each of these races has a single campaign in each StarCraft real-time strategy game. In addition to these three, various non-playable races have also been part of the lore of the StarCraft series; the most notable of these is the Xel'Naga, a race which features prominently in the fictional histories of the Protoss and Zerg races.