Protoss
Upon analyzing data from their most recent battles, the protoss have identified a few areas of improvement that would help them maximize effectiveness against their enemies. Based on their findings, the protoss have augmented their arsenal with a second psionic unit, a new way to counter flocks of Mutalisks, and a new form of enemy harassment.

Tempest
Description: The tempest is a new capital ship that deals massive area-of-effect damage to air units. It also has a standard ground attack, but its chief role is to help gain air superiority.

Oracle
Description: The Oracle is a psionic warship, built from a Stargate, that uses several unique abilities to raid and harass the enemy. The first is Entomb, which can temporarily block mineral fields from being harvested. Another ability, Preordain, grants vision of a targeted enemy building, allowing the protoss to see which units or technologies are being researched. Rounding out its kit is Phase Shift, which phases a target building, preventing it from being attacked, using its abilities, or granting technology. Not only can structures like missile turrets be prevented from attacking, but using this ability on a zerg Spire would block the production of Mutalisks, Corruptors, and air upgrades.

Replicant
Description: Replicants have one ability: to transform itself into any non-massive unit. They're expensive, so cloning a Zergling would not be very cost effective, but transforming into a specialized unit like a Raven, Infestor, or Siege Tank could open up interesting strategic options for the protoss.

New Abilities
A new ability called Arc Shield has also been added to the nexus -- this ability will temporarily add additional shield and building armor, as well as a weapon very similar to a photon cannon. The weapon does the same amount of damage as a regular photon cannon but only damages light units. This ability will help the protoss buy time to defend in the case of an unexpected drop from an enemy. Another ability, Mass Recall, has also been added to the nexus, which allows protoss players to teleport armies from out in the field back to the nexus. The recalled units are stunned for a few seconds when recalled.

Retired Units
As we add units to the multiplayer game, sometimes it’s necessary to remove units or alter others’ abilities to maintain game balance and eliminate redundancy. In the current design of Heart of the Swarm, the protoss are not able to deploy Motherships and Carriers, though these and other units that don’t exist in Heart of the Swarm multiplayer will still be available in Wings of Liberty multiplayer and the solo campaign.

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Terran
The resourceful terrans have also been improving their technology to better survive their battles in the Koprulu sector.

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.

Warhound
Description: 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.

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 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.

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Zerg
The zerg continue to evolve and adapt to changing environments, particularly the dangers they face on the battlefield. New creatures will help the zerg stage more effective sieges and add unique enemy-manipulating abilities to their arsenal.

Viper
Description: The Viper is a new flying unit with three unique abilities. Blinding Cloud temporarily reduces the attack range of all ground units inside the cloud to melee range, and prevents energy-based abilities from being used. Abduct allows the Viper to physically pull a unit to the Viper’s location. Finally, the Viper has a one-time ability called Ocular Parasite, which allows it to detach its eye stalk and meld it onto any friendly, non-massive unit, turning that unit into a detector.

Swarm Host
Description: The Swarm Host is a slow-moving ground unit that has no standard attack. When burrowed, the Swarm Host spawns a continuous stream of slow-moving melee units called Locusts that can be used to lay siege and pressure entrenched enemy positions.

New Abilities
The Corruptor's Corruption ability has been replaced by a new ability called Siphon that allows Corruptors to target buildings and slowly damage them. This damage is converted into resources for the zerg at the same time. Ultralisks have a new Burrow Charge skill that lets them dive underground and instantly surface at a target, allowing them to initiate the fight faster on a crowded battlefield. Finally, the Baneling has evolved tunneling claws similar to the Roach, which allows them to move while burrowed -- this new evolution will mean other races will need to be even more wary about hidden drops and making sure to have detectors with their army. Finally, the Hydralisk has a new upgrade that allows them to move faster while not on creep.

Retired Units
The Overseer has been cut; its detection ability has been replaced by the Viper and its Ocular Parasite.