This is a CO-OP vs AI. 4 Players can play at once but it works with only one as well. No computers are supported yet, and I do not think I will invest the time and effort into making it work.
The story is that the Protoss went to war with the Zerg and wanted to bring them down once and for all. However they managed to lose their Mighty Mothership to the Zerg. Kerrigan was there to destroy the Mothership, but instead she managed to take control over it. With the Mothership on the Zerg's side, they could start using different abilites from the Mothership and later on learned how to construct buildings from the Protoss.
Three weeks later the Protoss managed to locate the Mothership deep inside the planet Char. It was way too careful bringing in a big force this time, because it was so easily spotted, so they sent a small force to deal with them. However, the Zerg had way too good detection and managed to see the Protoss while they were moving out. They are now trying to stop you at all costs, no matter what.
The length of this game varies, but it may take up to 1 hour (game time seconds) to complete it. It has exciting features and a nice looking terrain as well.