StarCraft II: Heart of the Swarm is an expansion pack to the military science fiction real-time strategy game StarCraft II: Wings of Liberty by Blizzard Entertainment. Heart of the Swarm is the second part of a planned StarCraft II trilogy, with part three titled Legacy of the Void. The expansion includes additional units and multiplayer changes from Wings of Liberty, as well as a continuing campaign focusing on the Zerg race, following Sarah Kerrigan in her effort to regain control of the swarm and enact her revenge on the Terran dominion's supreme commander, Arcturus Mengsk. [wikipedia]