StarCraft II: Heart of the Swarm

StarCraft II: Heart of the Swarm is an upcoming expansion pack to the military science fiction real-time strategy game StarCraft II: Wings of Liberty and part two of the planned StarCraft II trilogy. Part three is titled Legacy of the Void.
The expansion will include additional units and multiplayer changes from Wings of Liberty, as well as a continuing campaign focusing on the Zerg species. It will span approximately 20 missions and will be priced as an expansion set. Heart of the Swarm is currently slated for a release on March 12, 2013

Gameplay

The game is expected to have around 20 missions, and will continue the story from Wings of Liberty, taking place two years after the previous game, in 2506. The player will play from the perspective of Sarah Kerrigan, recently returned to her human state by Jim Raynor.

Unit and ability changes

At Blizzard's 2011 BlizzCon conference, it was revealed that Heart Of The Swarm will feature 7 new multiplayer units, while removing  and changing the abilities of existing units and buildings. The exact modifications have since changed.
In a blog post, game director Dustin Browder explained the current status of the units announced at BlizzCon:

• The Terran race was originally expected to feature two new units: the Shredder, and the Warhound. Internal testing revealed the Shredder was too flexible and powerful, and it was therefore replaced by widow mines, mobile spider mines that fire missiles at the target, causing splash damage. The Warhound had an autocast ability which launches missiles that target mechanical units. During the closed beta, Blizzard agreed with pro gamers that it does not work in its current state. The Hellion will have a new battle mode added, which allows it to transform into a heavier and more powerful unit. In battle mode the Hellion will do increased damage but in an arc in front of it instead of in a line. The Ghost will have its "Cloak" ability changed to be a one-time cost for a time-based duration rather than a constant energy cost over time. Reactivating "Cloak" while calling down a nuke will not interrupt the nuke strike. The Battlecruiser gained a "Redline Reactor" upgrade which acted as a cooldown-based speed boost, instead, it will get an increase from 8 to 10 damage against ground. Lastly, the Reaper has its special building attack replaced by a passive health regeneration ability when out of combat, and also gains high-ground vision.

• The Protoss Replicant has been cut due to its tendency to stifle unit diversity, but the Oracle and Tempest remain. The Oracle provides several abilities that are useful for harassment such as slowing time in a circle preventing units form escaping, granting vision of enemy buildings and stopping buildings from researching or producing. The Tempest's role has changed since Blizzcon. While originally designed to provide large amounts of air splash damage, it is now an extreme long-range siege unit capable of hitting both the ground and air. A new caster called the Mothership Core has been added. The Mothership Core is a slow moving, flying unit that has three abilities. Purify allows the Mothership Core to gain a single target, long range energy attack, similar to the Photon Cannon. Mass Recall targets a group of Protoss units anywhere on the map and teleports them to the Core's location. Once the Fleet Beacon has been constructed, the Mothership Core can transform into the Mothership.

• Since Blizzcon, the Overseer has been re-added; the Viper and the Swarm Host also remain. The flying Viper has several abilities: "Blinding Cloud" which reduces the affected biological unit's range to 1, "Abduct" pulls a unit to the Viper's location, and the "Consume" ability allows the Viper to regain energy by siphoning health from a friendly structure. The Swarm Host periodically spawns slow-moving units called Locusts when burrowed. Locusts have range 2, and can hit ground. Ultralisks gain a "Burrow Charge" ability on a cooldown allowing them to quickly reach battle sites and the Hydralisk will have a researchable speed boost when traveling off-creep, once the Hive is built. Lastly, different types of Nydus worms are now planned. Some of the more effective worms that are being tested include ones that can quickly create a creep "highway," and another that can attack enemy buildings.

Plot

In the final series of missions in Wings of Liberty, Crown Prince Valerian Mengsk led a mission to Char in an attempt to reverse the infestation of the Queen of Blades, enlisting the help of General Horace Warfield and Rebel James Raynor. Despite incurring massive casualties, Valerian's expeditionary force managed to successfully employ a Xel'Nagan artifact, which resulted in the deinfestation of the Queen of Blades. Mindful of Zeratul's prophetic warning concerning Kerrigan's importance in countering the rising threat of the Protoss/Zerg Hybrids, Raynor defends Kerrigan from Tychus' attempt to kill her, shooting Tychus in the process. The closing scene showed Raynor carrying Sarah Kerrigan across the battlefield in his arms with Valerian Mengsk's Dominion fleet descending upon Char overhead.
Further introduction to the plot of Heart of the Swarm is given in the StarCraft II novel by Christie Golden, StarCraft II: Flashpoint, which is stated to "tie in with the events" of the game. On Char, Raynor manages to save Kerrigan and take her back to the battlecruiser Bucephalus, but is forced on the run from Arcturus Mengsk and the undamaged half of the Dominion fleet. After hiding at Deadman's Port and being ambushed by one of Mira Han's henchmen, Raynor's Raiders and Valerian finally take Kerrigan to see Emil Narud, a specialist on Zerg and leader of the Moebius Foundation. However, Narud reveals his alignment with Emperor Mengsk, and unleashes powerful Hybrids under his command, enabling him to run with the Xel'Naga artifact. Raynor rescues Kerrigan and the rest of the Raiders, and together with Valerian they manage to escape to a secret Umojan facility where Kerrigan can be treated, and their battlecruisers repaired.
The plot of Heart of the Swarm starts shortly after the events of Wings of Liberty. It will focus on the Zerg race and feature Sarah Kerrigan as the protagonist and anti-hero. The campaign begins with Kerrigan's quest to assume leadership of the swarm in her regained human form and exact her revenge on Arcturus Mengsk, Emperor of the Terran Dominion. The Zerg have split into several factions without her leadership, and she must take control of the various rival broods, headed by powerful queens, while General Warfield of the Dominion is attempting to eradicate the Zerg on Char. Additionally, a teaser trailer for the game shows Nova leading a team of Terran Ghosts to infiltrate a Terran facility and ordering them to "find Kerrigan." Amidst the chaos of the attack, Raynor chases a pair of Ghosts to a room. The Ghosts lock the door behind them, and soon after an explosion occurs. Raynor then picks up the ruin of the door and enters the room where he finds Kerrigan wearing a Terran Ghost suit, her back to him.

Development

The development of StarCraft II was announced on May 19, 2007, at the Blizzard Worldwide Invitational in Seoul, South Korea. At the June 2008 Blizzard Worldwide Invitational, Blizzard Executive Vice President Rob Pardo said that StarCraft II was to be released as a trilogy of games, starting with Wings of Liberty, focused on the Terrans, followed by Heart of the Swarm, revolving around the Zerg, and finally Legacy of the Void, devoted to the Protoss. Blizzard's storyboard team was already working on Heart of the Swarm in early 2010 while Wings of Liberty's gameplay was refined. Wings of Liberty was released July 27, 2010 to much critical acclaim.
Blizzard had never anticipated releasing Heart of the Swarm before the end of 2011. By March 2011, lead designer Dustin Browder estimated the game was "about a year" from completion. By July 2011, the first portion of the game was finished, as well as many of its cinematic cutscenes.
A few updates will be made to the game's graphics engine, including upgrades to the look and behavior of Zerg creep, as well as some improvements to the rendering of game environments. However, the expansion will have the same hardware requirements as Wings of Liberty.
On April 30, 2012, Blizzard announced that the latest multiplayer build of Heart of the Swarm would be playable at the MLG Spring Championship (June 8–10) ahead of a planned beta release. No actual release dates were specified.
As of June 15, 2012, the game is complete. The only unfinished thing is "tuning and polishing". No release date was specified.
August 15 Blizzard announced that the multiplayer beta will be beginning soon. As of September 4, 2012, Blizzard began closed beta testing of the multiplayer beta, releasing it to select Pro-gamers, members of the press, Arcade contest winners, and shoutcasters. The beta testers are not under a non-disclosure agreement, so they are free to stream their games, release pictures, etc.
On their website, Blizzard has stated that the official release date for Heart of the Swarm will be March 12, 2013.

References :

http://en.wikipedia.org/wiki/StarCraft_II:_Heart_of_the_Swarm

https://eu.battle.net/account/activation/landing.html?product=S2&purchase&utm_source=internal&utm_medium=Blizzard_com&utm_campaign=HotS_Presale&utm_content=Standard_version