Synopsis

Characters and setting:
The campaign storyline of StarCraft II takes place four years after StarCraft: Brood War, and features the return of a number of characters from the original series, including Zeratul, Arcturus Mengsk, Artanis, Sarah Kerrigan, and Jim Raynor. Players also revisit the original series' worlds, like Char, Mar Sara, and Braxis, as well as new worlds, such as the jungle planet Bel'Shir. It has been confirmed that the Xel'Naga, the ancient space-faring race responsible for creating the Protoss and the Zerg, plays a major role in the story.

At the conclusion of Brood War, Kerrigan and her Zerg forces became the dominant faction in the Koprulu Sector, having annihilated the United Earth Directorate's Expeditionary Force, defeated the Terran Dominion, and invaded the Protoss homeworld of Aiur. However, after the conclusion of Brood War, Kerrigan retreats to Char, despite having more than enough power to crush all remaining resistance in the Koprulu Sector. In the four years leading up to the events of StarCraft II, she has not been seen or heard from by any of the other characters, although her ultimate attack may come at any moment.

Arcturus Mengsk has been left to rebuild the Dominion, and is consolidating his power while fending off harassment from rival Terran groups. Valerian Mengsk, a character introduced in the novel Firstborn, will play an important role in Dominion politics, due to his position as heir apparent to the throne. Meanwhile, Jim Raynor, whose role in the events of StarCraft and Brood War has been marginalized by the media under the Dominion's control, has been reduced to mercenary status, and has been shown to be doing business with the "Moebius Foundation", a new faction which is interested in ancient Xel'Naga artifacts. Chris Metzen, Vice President of Creative Development at Blizzard, has emphasized that by the events of StarCraft II, Raynor has become jaded and embittered by the way he was used and betrayed by Arcturus Mengsk. Other new characters to the series include Tychus Findlay, first introduced in the StarCraft II teaser cinematic, a marine who will be a member of Raynor's crew, and Matt Horner, Raynor's second in command, a character originally featured in the novel Queen of Blades.

Following the fall of Aiur and the death of their matriarch Raszagal, the Protoss have retreated to the dark templar homeworld of Shakuras. There, Artanis, a former student of Tassadar, is trying to unify the Khalai Protoss and the dark templar, who have nearly separated into a tribal mindset as a result of centuries of distrust. Zeratul, tormented over the murder of his matriarch, has disappeared to search for clues to the meaning of Samir Duran's cryptic statements regarding the Protoss/Zerg hybrids in Brood War's secret mission "Dark Origin".

Plot:
Four years after the Brood War, the Dominion is once again the dominant Terran power in the Koprulu sector. For reasons unknown, Kerrigan gathered the swarm at Char and has vanished from sight. With the Zerg gone, the Protoss have once again taken a passive role in the galaxy. Jim Raynor has formed a revolutionary group named Raynor's Raiders in order to overthrow Dominion Emperor Arcturus Mengsk.

On Mar Sara, Raynor meets with an old comrade, Tychus Findlay. Together, they liberate the local population from Dominion control and also discover a component of a mysterious Xel'Naga artifact. As the Zerg begin to overrun Mar Sara, Raynor arranges an evacuation to his battlecruiser, the Hyperion, captained by Matt Horner.

The Raiders embark on a series of missions to find the remaining pieces of the Xel'Naga artifact, which they sell to the enigmatic Moebius Foundation in order to fund their revolution. Along the way, they meet with Gabriel Tosh (a Spectre, or psychic assassin), and colonist leader Ariel Hanson. The Raiders perform missions to help Tosh procure the raw materials to train new Spectres. They also aid Hanson as she attempts to evacuate her colonists who are caught between the Zerg infesting their planets and the Protoss attempting to eradicate the infestation. Matt Horner also arranges a series of missions to undermine Mengsk with the eventual goal of overthrowing the Dominion. Finally, Zeratul sneaks aboard the Hyperion to deliver a psychic crystal which allows Raynor to share visions involving a prophecy regarding the future of the Zerg and Protoss and a mysterious hybrid of the two, the ultimate revelation being that only Kerrigan has the power to prevent the eradication of all life in the sector and beyond.

After collecting the final artifact piece Raynor's forces encounter Dominion battleships at the pre-agreed Moebius Foundation rendezvous point. The Moebius Foundation is revealed to be under the control of Valerian Mengsk, Arcturus' son. Valerian, intending to show himself as a worthy successor to his father, asks Raynor to help him invade Char and use the artifact to restore Kerrigan's humanity, thus weakening the Zerg. To the initial dismay of the crew, Raynor agrees. As the invasion of Char begins, the Dominion and Raider fleet is severely damaged by the heavy Zerg defenses. Raynor secures a foothold on Char and rendezvous with Dominion forces which survive the crash landings. The combined forces push towards the main Hive Cluster of the planet, protecting the artifact which eventually reaches full power and activates destroying all Zerg within its blast radius. Raynor's team finds Kerrigan restored to human form; however Tychus reveals that he made a deal with Arcturus Mengsk: trading Kerrigan's life for his own freedom. Raynor defends Kerrigan from Tychus' attempt to kill her, shooting Tychus in the process. The closing scene shows Raynor carrying Sarah Kerrigan across the battlefield in his arms.