IRVINE, Calif.--Blizzard ended months of Starcraft II silence at its headquarters today. We hadn't gotten the slightest morsel of new info on the famed developer's rabidly anticipated strategy sequel since BlizzCon in August of 2007, but now we've finally gotten our hands on the new and improved zerg, the third and last of Starcraft II's factions to be revealed to the press. After sliming our way through numerous multiplayer games with the zerg, we can say that our previous experience with the terran and protoss factions in Starcraft II still holds. Everything old here is new again, which is to say that the zerg feel startlingly similar to their counterparts in the first game. Of course, when you're building on arguably the best strategy game ever made, that's really not such a bad thing.

　　Before we got our hands on the game, Blizzard showed us a brief cinematic movie that depicted the zerg's conquest of the galaxy. This short movie was accompanied by a voice-over from Kerrigan, the zerg's iconic and mutated human-hybrid queen. Though we didn't see what physical form she'll take in the final game, Kerrigan spoke extensively about the zerg's several-years-long absence from the galactic scene and the "evolving" that's occurred in that interim. She concluded by saying that the zerg are about to become much greater and referred to a "final metamorphosis" that's only just begun. Clearly this portends ominously for the events of the single-player campaign.

　　As before, winning with the zerg is all about superior numbers.

　　Too bad, then, that Blizzard wasn't addressing any aspect of Starcraft II's storyline today. But that's OK; we had enough to take in just absorbing all of the changes to the zerg's tech tree. Let's start with what's the same, though. The zerg will use a building model nearly identical to that of the first game. All zerg units are birthed from the larvae that will spawn automatically from your hatcheries, and all structures grow out of the basic drone worker units. Like the terrans and protoss, the zerg will also collect crystal and vespene gas resources in the traditional manner, and you can build structures only on the ooze-like purple creep that spreads out around a zerg hatchery.

　　Where the zerg differ is in their specific lineup of units and tech-tree progression, most of which is new since the first Starcraft. Some of the basic units, like the zergling and hydralisk, function more or less the same, but Blizzard says more than half the units are new, and even most returning ones have some sort of modification. There's a new ground attack unit called the roach that regenerates health at incredible speed. Many enemy units simply can't kill the roach in one-on-one combat because the roach heals faster than the opponent's ability to dish out damage. The only real way to deal with a flood of roaches is with focused heavy fire, and we found a mass of them to be devastating against an unprepared enemy.

　　There's a devious new support unit called the infestor that can move while burrowed underground, and it can unleash some of its nasty abilities without having to surface. Taking a cue from Blizzard's early presentation, we tried having a handful of burrowed infestors sneak right underneath an enemy's base defenses, and then had them unleash their infestation ability once in the middle of the base. This overtakes one structure, preventing it from producing units and spawning a host of infested terran marines from it to cause havoc. Though these zombie marines don't do a lot of damage, they made for the perfect distraction. While our enemy was busy trying to handle the mess within his own base, we brought our main attack right to his front door and waltzed on through. Burrowed infestors are easily spotted by any sort of detection, so you'll have to be careful where you take them.

　　The roach and the infestor are just two of the zerg's nasty new units.

　　By far our favorite zerg unit was the queen, of which you can only make one. There were queens in the original Starcraft, but she's changed so much here that she might as well be new. The queen is a large defensive unit that skulks around your base and provides all sorts of interesting defensive abilities. She can build tiny turrets on the creep almost instantly, and then a detecting supplemental unit called the shrieker that increases the range of those turrets. You can make the queen evolve and increase in size, too, which confers more abilities. After evolving, the queen can infect a small part of the creep; tunnel from the creep to any other zerg building on the entire map; or even heal a zerg building for most of the value of its health. She's also a formidable melee fighter when it comes to base defense. It seems as if the queen will be a deadly unit in the hands of a player with strong micromanagement skills.

　　Some of the old, familiar units are quite different, too. The overlord is no longer a detecting unit, and it can't carry other units for transport. Instead, it can infect resources such as minerals and make them inaccessible, and it can spit creep onto most parts of the map. The overlord can also evolve into another flying unit called the overseer that can detect hidden enemies. The bull-like ultralisk now has an area-of-effect element added to its already considerable melee attack, which we found especially potent when tackling our enemies' base defenses.

　　True to its word, Blizzard has made the zerg gameplay all about overwhelming numbers, similar to the way it was in the first game. We can't speak to the skill of our opponents today--fellow members of the international games press, mostly--but we found that the key to victory was generally to crank out as many roaches, hydralisks, ultralisks, and other creepy-crawlies as we could and simply win through attrition. And though we were no doubt playing on top-of-the-line gaming hardware, we were at least heartened to see that the frame rate didn't suffer an iota, even when we flooded the screen with scores of units engaged in frenzied battle.

　　Blizzard has made a lot of other additions to Starcraft II's gameplay since we last saw it. There are now high-yield minerals on the map, which are yellow in color and offer greater stores of resources than the blue kind. There are also destructible obstacles such as rocks now blocking many choke points; you can attack and demolish these roadblocks, but they take a lot of work to get rid of. Similarly, there will be other obstacles like trees and shrubs that will block your line of sight, which lets units hide behind them. Lastly, we noticed a few of the new xel'naga observation towers, which you can activate by touching with a single unit. These will give you a big radius of sight around them while active, though they'll shut down once you move your unit away.

　　Blizzard will likely spend months just balancing the three factions against each other.

　　It's worth noting that just about anything you read about here is subject to change before Starcraft II finally ships, whenever that is. Blizzard reps talked about one gameplay mechanic in the build we've played today that has changed drastically three or four times in the last two weeks. The company is famous for iterating and rebalancing ad infinitum until the gameplay is spot-on, so what we played today may vary significantly in a few ways, or a lot of ways. We hope at least that the basic zerg framework is pretty well locked down now, though; we were quite happy to see some grotesque old friends back in the fray after all these years.