Kerrigan will be a playable unit in most missions of StarCraft II: Heart of the Swarm. When the former Queen of Blades takes the field, she has multiple roles to choose from. Each role is called a Battle Focus and comes with a a unique set of abilities. As the campaign progresses, new roles will unlock, and Kerrigan will acquire new abilities for existing roles. The Battle Focus you choose for Kerrigan in any given mission and the way you use her powers will have a major impact on how each mission plays out.
Harder, better, faster, stronger: the Swarm never stops evolving, and in Heart of the Swarm, you decide how the zerg develop. Between missions, you'll be able to mutate your different zerg species. If you unlock enough mutations for a species, you can evolve that species into one of two different strains. For example, one zergling strain might evolve the ability to hatch more zerglings from the same egg, while the other could produce zerglings that can make short leaps forward to close into melee distance more quickly.

"It's logical." Mr. Spock
(Sorry. Wrong Universe)
also next time i see Jay Wilson working on a project i will not buy it dont care how good the game looks its clear that he has no idea what hes doing and what people want from a game ,it seams he just makes a game that he likes and doesn't care what the customers want
Blizzard please just get rid of him
in South Korea people literally broke into blizzard HQ and Stole all files of Evidence they could find to See if blizzard or Actavision was breaking any of their Fair trade contracts. and it also seems That even more People are mad about this. I only hope they do Try to do something better then removing the Carrier... Afterall its the Symbol of the Protoss. it would be alot better to just buff them. give them some new good Features. the Protoss feature's and Gimmicky is BAD right now. Even Husky talked about it and gave protoss a 2/10 and that's bad! because they are only adding More ball of Death Feature's to it and Block Mineral Lines??? that's not even Op that's Just BROKEN!!!
that's broken beyond. they should not add so many Control Type features. this needs to be skill based... not like HEY I CONTROL YOUR ARMY AND NOW IT DIES LOL!!!
please Blizzard STOP THAT!!!
Off the top of my head I can think of the "evil" ghosts (I cant remember the name for them) that you unlock in story mode and the aoe ground attack panther that you get with research samples. None of them are available for PvP.