Among BlizzCon 2011's hubbub came perhaps the most heralded bit of news from the event: solid details regarding Heart of the Swarm, the first of two expansion packs for Blizzard's best-selling StarCraft II real-time strategy game.

And where the stereotypical view of a video game's "expansion pack" seems to generally include a few new units and several new levels to play on, Blizzard seems to be crafting a follow-up to StarCraft II: Wings of Liberty that's as detailed and content-rich as Wings of Liberty itself.

Picking up where Wings of Liberty left off, Heart of the Swarm takes a full look at the life of Sarah Kerrigan both during her reign as the Queen of Blades/leader of the Zerg as well as her present, wherein the character has been returned to a human form (though with some remaining psionic abilities), resumed her previous occupation as a Ghost operative and has begun to join Jim Raynor in his fight against the Zerg.

Sarah Kerrigan returns to human form and her Ghost profession in the StarCraft II: Heart of the Swarm expansion pack.

While no set date has been released regarding Heart of the Swarm (the ground rule being that Blizzard releases titles, expansion packs and updates when it feels they're ready and not a moment before), the genuine shock and excitement seemed to come from the multiplayer side of StarCraft II, which is looking at a hefty overhaul upon the release of Heart of the Swarm. With the Heart of the Swarm expansion pack, players will find some of their most familiar units changed, removed, replaced or updated, the company citing that it was looking for added balance in its multiplayer gameplay as well as having noticed some units that were either too costly or rarely used during studies of thousands of multiplayer matches.

Breaking it down on a race-by-race basis, here's what you can expect to see as of BlizzCon 2011 (keep in mind that things can and do change with the game's development and nothing is set in stone):

Terran:

The Hellion will be able to transform into a full-scale robot in Heart of the Swarm. And that's pretty darn cool.

- Hellion: Upon studying multiplayer game sessions, the development team noticed that the fast, speedy Hellion was almost solely being used as an early game unit and essentially abandoned during mid and late-game use. Blizzard will be changing this with the Heart of the Swarm expansion, allowing the Hellion to change from its vehicle form into a slower, tougher robot to help defend against tougher enemies as the round progresses.

The faster, lighter Thor-based mech of choice: the Terran Warhound.

- Warhound: If you've played as the Terrans, you know that the Thor battle mech is amazing, but slow to create and costly. The Warhound, which arrives with the Heart of the Swarm expansion, will be available as a smaller, faster version of the Thor and specialize in anti-mech combat perfect for destroying other robots or vehicles in a pinch.

The big papa that is the Thor mech has its aerial attack removed but gets a better ground attack in Heart of the Swarm.

- Thor: While the Thor will essentially remain the same, Blizzard will be instituting a restriction in which a player can only create and use a single Thor at any given time. The company will also be removing its anti-air cannons but implementing a specialized ground attack that can act as an effective mortar.

The Terran Shredder, a wonderfully radioactive base defense unit en route to the Heart of the Swarm expansion pack.

- Shredder: After years of watching original StarCraft and StarCraft II: Wings of Liberty multiplayer games, Blizzard noticed that many players like to send a kludge of mixed units (a.k.a., the "Ball of Death") against their opponents, the mix of units ensuring that their opponents would have a harder time identifying and targeting the most dangerous units in the group. With this in mind, the Terran forces will be receiving the Shredder, a defensive unit that pops up and emits massive amounts of radiation whenever enemy forces approach. Keep in mind that the Shredder will become inactive if units from its own armies are within a given range, so there's give and take to the new unit, as powerful as it may be. The Shredder will also be a reparable unit, so if damaged, multiple SCV units can quickly swoop in to fix a damaged Shredder and get it ready to repel the next wave of attacks.

Don't worry, it's lost weight and will be a bit faster this time around.

- Battlecruiser: While this will remain the Terran capital ship, it's finally getting the speed boost you've always wanted. And this is never a bad thing.

The Terran Reaper: Now with a better health insurance policy.

- Reaper: You love 'em, but you know they're fragile. Following the Heart of the Swarm expansion, the Reaper will finally be able to regenerate when not in use.

Protoss:

Sadly, the Carrier has been nixed for Heart of the Swarm (though you can still check for used ones on eBay).

- Carrier: As of this point, the Carrier will no longer be available for Heart of the Swarm multiplayer gameplay, the company citing its high cost and slow build speed as an impediment to its use during matches.

It was fun while it lasted: say goodbye to the Protoss Mothership in the Heart of the Swarm expansion pack.

- Mothership: It was great, it was powerful, it was incredibly expensive to build and it won't be around for Heart of the Swarm. Like the Carrier, Blizzard will be cutting the Mothership and transferring its abilities to other units.

Attack both air and ground units with ease with the Protoss Tempest capital ship.

- Tempest: Even if the Carrier and Mothership are headed to the dust bin, Blizzard announced that it's working to create the Tempest, a new, lower-priced capital ship complete with anti-air and ground assault abilities.

Take control of the skies and wreak havoc with the Protoss Oracle.

- Oracle: Another new Protoss air unit, the Oracle can cast temporary shields around enemy resources being harvested as well as use a Preordain ability to take a peek at what units, resources and technologies are being looked into on your opponent's end. These abilities are rounded out by a Phase Shift function, which renders a target effectively useless and prevents it from being attacks as well as producing units, researching new technologies or anything else while the Phase Shift is in effect.

Happily clone your opponents' forces for your own ends with the Protoss Replicant.

- Replicant: Perhaps the most devious new unit en route from the Heart of the Swarm expansion, the Replicant, though expensive to produce, will be able to make a perfect copy of any unit, including those of your enemies. With a little imagination, you'll be able to use the Replicant to copy one of your opponents' workers, thereby allowing you to create an army of both your own units and their units to fight them with, something that opens the doors to a lot of new possibilities.

The Protoss Nexus will be able to take care of itself a bit better thanks to new abilities in Heart of the Swarm.

- Nexus: Though relatively the same, the Protoss Nexus can now deploy Arc Shields to other Protoss buildings, which lets you transfer a limited-time additional protection as well as Photon Cannon-like offensive capability. This in turn could buy you some extra time to get your army out the door and in the fight.

Zerg:

It may not be adorable, but it WILL be useful: launch hordes of Locusts at your opponents with the new Zerg Swarm Host.

- Swarm Host: The Zerg have never really had an artillery unit to speak of and Blizzard meant to rectify this. The Swarm Host is a new type of unit that will be able to approach an enemy base, burrow underground, then release wave after wave of Locust units which will run up to an enemy structure and explode against it. While the Locust units themselves aren't terribly powerful, the Swarm Host will keep releasing the units until discovered and destroyed, thereby creating additional problems for opponents.

Aerial combat will get a bit more interesting thanks to the Zerg Viper.

- Viper: A new Zerg flying unit capable of using a Blinding Cloud ability to severely impair the vision of its opponents as well as temporarily locking out any energy-based attacks that can be used against it. The unit can also use an Abduct ability, which functions as a long, extended tentacle capable of grabbing enemy units and pulling them closer to destroy. Finally, the Viper's Ocular Parasite ability allows friendly units to detect otherwise invisible opponents, giving them an edge in perceiving what's around them.

Get ready to face some burrowing Ultralisk charges in the Heart of the Swarm expansion.

- Ultralisk: While these units will essentially remain the same, Blizzard will be incorporating a change that will allow them to charge their opponents while burrowed.

The 2012 Zerg Baneling, now with an awesome burrowing movement feature!!!

- Banelings: The beloved Zerg Baneling suicide unit will be allowed to move while burrowed, thereby bringing them that much closer to the units and bases they're trying to destroy. Fun for you, a headache for your opponent and a welcome change for many.

Have some extra energy? The Corruptors will gladly siphon it in the Heart of the Swarm expansion pack.

- Corruptor: Although they'll remain pretty much the same, the Heart of the Swarm expansion will allow Corruptors to siphon energy from other units to keep themselves alive.

Even if the typical video game expansion pack isn't expected to deliver more than a dozen new levels and a few new units to play with, Blizzard seems to be working on something interesting here. In an interview with company personnel, Blizard developers stated that players could expect approximately 20 new missions and side missions, or a full campaign experience. Where Wings of Liberty mainly focused on the Terran side of things, Heart of the Swarm will be predominantly Zerg and will offer new units to play with, the game allowing the Zerg to be upgraded by absorbing the DNA and abilities of slain opponents.

In addition to the new units and changes, developers stated that they were working to alleviate the learning curve of the Zerg forces and offer a campaign that was slower paced in some respects as a means of teaching newer players how to use the units. Where Wings of Liberty generally offered a "new-mission-new-unit-to-work-with" sensibility, Heart of the Swarm should break from this and offer players an easier working pace to play with, something which should be a welcome change.