The third and final chapter of Starcraft II is named the Legacy of the Void which is a science-fiction-themed real-time strategy game for PC and Mac platforms. When playing Starcraft you will take control of the psionic Protoss faction in an all out interstellar war against the Zerg and hardy and resourceful terrans. The Zerg are a race entirely unlike the Terrans or the Protoss, they are composed of many different species integrated into the Swarm via a Zerg infestation. The Zerg are rapidly and selectively evolved into deadly and efficient killers with one goal in mind, absolute,and total domination. The Zerg make no use of technology to create their weapons, armor, or starships. Instead, these functions are efficiently fulfilled through biological adaptation and planned mutation of the Zerg strains. Even Zerg buildings are in fact specialized organs within the living, growing organism of a Zerg nest. The terrans are newcomers to the Koprulu sector. Terrans are the direct descendents of a disastrous expedition launched from planet Earth centuries ago. The crew of the failed doomed mission were expendables. Those that survived established three colonies that became the basis for the major power blocs in terran space: the Confederacy, the Kel-Morian Combine, and the Umojan Protectorate. The corrupt Confederacy was overthrown by terrorist and revolutionary Arcturus Mengsk during the chaos of the zerg invasion. Now the Terran Dominion has emerged from the ashes of the old Confederacy as the dominant power, ruled by none other than Emperor Arcturus I. The Terrans were forced to adapt to the harsh existence on the mostly lifeless worlds of the sector, the terrans are masters of survival. With neither the advanced technology of the protoss nor the natural prowess of the zerg to rely on, the terran military forces consist of a varied mix of units. From basic but effective infantry like the Marines to heavily armed battlecruisers, terran units rely on solid armor, plentiful firepower, and strength in numbers to hold the line. Terrans excel in defensive situations where their bunkers and Siege Tanks really shine. Legacy of the void is set chronologically after Starcraft II: Wings of Liberty, the Terran campaign, and Starcraft II: Heart of the Swarm, the Zerg campaign. All current development was focused on the first chapter, Wings of Liberty, until recently so only a vague understanding of the plot of the second chapter, Heart of the Swarm, exists, and next to nothing is known for certain about Legacy of the Void except that it will be from the perspective of the Protoss faction. It has been confirmed that Wings of Liberty will serve as the "core" Starcraft II video game, with Heart of the Swarm and Legacy of the Void serving as expansion packs. It has been officially confirmed that it will not be possible to play the Zerg or Protoss campaigns without already having purchased the Terran campaign.