Blizzard Entertainment announces the Heart of the Swarm expansion is now available for StarCraft II, their sci-fi RTS sequel. "Heart of the Swarm enhances every aspect of StarCraft II," said Mike Morhaime, CEO and cofounder of Blizzard Entertainment. "In addition to Kerrigan’s campaign and the new multiplayer units and maps, we think players will really enjoy the new online elements and new features that make StarCraft II more fun and easier to learn than ever before." The announcement outlines the perks for buying the various editions of the add-on, and here's an overview:

Heart of the Swarm picks up the story where StarCraft II: Wings of Liberty® left off, focusing on Kerrigan’s quest to reunite the Swarm and exact revenge on Arcturus Mengsk. Over the course of 20 campaign missions, players will follow Kerrigan as she sweeps across the galaxy, incorporating a variety of distinctive zerg species into her brood. Kerrigan will grow in strength from mission to mission, and players will be able to customize her with powerful new abilities, as well as evolve various zerg strains into fearsome new subspecies to suit their play style.

New weapons of war also debut in Heart of the Swarm’s multiplayer, including new units such as Terran Hellbats, Zerg Swarm Hosts, and Protoss Tempests, while certain existing units from Wings of Liberty will be updated with new capabilities. In addition, several new features will enhance the game experience, including group and clan systems; training and versus-A.I. modes, to help new players transition from the campaign into multiplayer; unranked matchmaking; Global Play, enabling players to battle others in different regions around the world; additional stat tracking; user interface improvements; an enhanced physics system, for more visceral-looking battles; “Watch With Others” and “Take Command,” to watch replays with friends as well as jump in and assume control at any point; a leveling system that gives Heart of the Swarm players a new way to earn customization options for their online profiles; and much more.