The second installment of StarCraft II, called Heart of the Swarm, will feature an entirely new single-player campaign focusing on the Zerg faction. Blizzard talked about how that will work previously, but to date hasn't revealed much about how the multiplayer part of the game will be changing. We can expect concrete details at BlizzCon 2011 later this October, but in the meantime, Blizzard is sending out teaser images for some of the new units...