In StarCraft, Jim Raynor begins the campaign on Mar Sara.
Mar Sara is a Terran-owned frontier colony and the setting for the opening missions of Episode I. Raynor is introduced there as a marshal dealing with Zerg attacks and the increasingly harsh response of the Terran Confederacy.
The planet is important because it brings Raynor into contact with the Zerg, the Protoss, and Arcturus Mengsk’s rebellion. The events on Mar Sara also establish Raynor’s distrust of Confederate leadership and begin his transformation from local lawman into a major military figure.
Mar Sara is sometimes confused with Tarsonis, the Confederate capital world, or Korhal, the later political center of Mengsk’s Dominion. It is also distinct from Char, the Zerg-dominated world associated with Sarah Kerrigan and the Overmind.