New Unit:Widow mine

Widow mine is a new Unit in SC2:Heart of the swarm! Its look a spider and can borrow themselves down in the ground and exlodes if something walk on them. Abilities: Attacks air and ground. Large explosion raidius.

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New Unit: Battle Hellion

A battle Helion is a upgraded Helion, who also existed in SC2- The wings of liberty. But in the new expansion you can upgrade your helions to battle helions.When you have upgraded to a Battle Hellion, you get:

-Transformation
-Area-effect flameweapon
-Though close combantant.

They will be strong aginst massunits like Marines, Zerglings, Zealots etc   .http://www.youtube.com/watch?v=DbXBydTTLwM

New Terran abilities

The Hellion has been upgraded to a transforming unit similar to the Viking. When transformed into its new battle mode, the Hellion will gain in hit points and get a stronger flame attack that covers a short arc in front of it. This makes the Hellion more effective in late-game fights against large clusters of light units such as Zealots. The Ghost’s Cloak ability has also been modified — it will no longer be a toggled effect. Instead, there will be a one-time energy cost to activate Cloak for a specific time duration. Energy regeneration will continue while cloaked, and Ghosts can re-cloak while nuking without interrupting the call-down. The Battlecruiser will gain a speed-boost ability called Redline Reactor, which is governed by a cooldown. And finally, the Reaper no longer has a special building attack, but instead has a passive health-regeneration that allows it to recharge hit points quickly when out of combat.

New Unit: Thor (Modified)

Thor (Modified)Description: While it was always quite effective against ground and air, one of the biggest problems with the Thor has been that it’s too big and bulky to move around well… so the terrans decided to made it even bigger. In Heart of the Swarm multiplayer, terran players will be limited to having only one Thor at a time, but this new behemoth hits even harder with its regular ground weapons and can absorb a tremendous amount of damage. The terrans have also swapped out the Thor’s anti-air weapons for a bombardment ability that does a huge amount of damage to a wide swath of ground. The Thor will need time to set up its bombardment cannons, as well as time to repack them after an attack, much like a Siege Tank. Of course, fielding such a powerful weapon requires a hefty investment in technology, so both an Armory and a Fusion Core will be required before a Thor can be built.

New Unit: The Shredder.

Description: The Shredder is a new unit built from the Factory that allows the terran player to control the battlefield. In its mobile form, the Shredder has no attack — but when set to stationary mode, it channels area-effect damage to both the air and ground. If a friendly unit enters the range of the Shredder, the weapon shuts off.  http://www.youtube.com/watch?v=axVMWSJS3ho

New Unit:Warhound

WarhoundDescription: The Warhound is a small, walking ground mech that wields an effective anti-air weapon with splash damage, much like the Thor from Wings of Liberty. The difference is that the Warhound is smaller and much more nimble, though it gives up some range on its anti-air missiles in exchange for this mobility. The Warhound also wields a small ground attack weapon that does additional damage to mechanical units, making it particularly well suited to taking out enemy Siege Tanks — though it’s not particularly effective against non-mechanical units.

http://www.youtube.com/watch?v=H3Bh6UBQ1Y8