Participating players will get a first look at StarCraft 2: Legacy of the Void, the third installment of the game trilogy, when the closed beta starts on March 31st. The Blizzard blog post announcing the closed beta notes that there have been a lot of changes since the game was first shown at last year's Blizzcon. In preparation, Blizzard produced a video detailing some of the changes, which range from resource management to some new units. 

New units include the Adept and Disruptor for Protoss; a killer mobile factory called the Cyclone for Terrans, and the Lurker and Ravenger for Zerg. These are in addition to returning units, which have been tweaked for the new games. A full summary of their abilties can be found on the blog. Another Terran unit is in the works, and Blizzard has expressed interest in working with the community to develop one that helps round out humanity's army.  

Closed beta players will also have a chance to try out the two-player Archon Mode. This is a cooperative mode where two players control the same army, which gives new players a chance to learn from experienced ones. Or at least new opportunities to mess up each other's games. Whichever works.

The closed beta starts on March 31, and invitations should be send out soon.