The following section contains information from a previous version of StarCraft II: Heart of the Swarm which is no longer valid.

The evolution pit underwent considerable change during the development of StarCraft II: Heart of the Swarm.

EvolutionChamber HotS Game1

The evolution pit

Formerly called the evolution chamber,[1] the structure enabled changes to units.

Each unit featured three upgrades and a final, irreversible choice. For instance, the zergling can get the Metabolic Boost, Posthumous Mitosis, and Rapid Genesis upgrades. Afterward it could become a raptor (which gains combat bonuses) or a swarmling (which spawn 3:1).[2]

As zerg units were unlocked/developed, they would fill up the evolution pit—similar to the armory from Wings of Liberty.[3] These mutations were made "on the fly" during gameplay.[4]



MetabolicBoost SC2 Zergling
Metabolic Boost
  • Increases zergling movement speed. The zerglings "grow wings".
Campaign Acquisition
Acquired from Evolution pit
Purchased from Spawning pool
Hotkey M
Cost 100 Minerals Terran SC1 100 Gas Terran SC1 79Time SC2 Game1
Posthumous Mitosis[2]

Zergling has a 20% chance to spawn 2 broodlings on death.[2]

Rapid Genesis[2]

Zerglings train instantly.[2]

Evolve Zergling[2]

Zerglings can transform into either raptors or swarmlings; once made, the choice is irreversible.[2]



Viscous Discharge[2]

Baneling acid slows move speed of all units hit for a short period of time.[2]

CentrifugalHooks SC2 Game1
Centrifugal Hooks
  • Increases the speed of banelings.
  • +Increase the health of banelings by +5.
  • Causes banelings to roll instead of walk.
Purchased from Baneling nest
Hotkey C
Cost 150 Minerals Terran SC1 150 Gas Terran SC1 79Time SC2 Game1
Required Lair

Baneling splash radius increased by 25%.[2]

Evolve Baneling[2]

Banelings can evolve into either gorgelings or splitterlings; once the choice is made, it cannot be reversed.[2]



Chitinous Plating[2]

Roaches gain a +1 bonus to armor.[2]

Bile Ducts[2]

Roaches gain a +2 bonus to damage.[2]

Organic Carapace[2]

Roach regeneration increases by 2 hp/second.[2]

Evolve Roach[2]

Roaches transform into leeches or prowlers; once the choice is made, it cannot be reversed.[2]


Co-op MissionsEdit

In Co-op Missions, earlier in development Abathur was to have the evolution pit as a unique structure, similar to Karax and the solar forge. The evolution pit would have contained researchable upgrades to improve Abathur's toxic nests, locusts, and the symbiote mechanic that was removed later in development.[5]


  1. SoMuchMass. 2011-10-22. BlizzCon 2011 - Starcraft 2: Heart of the Swarm - Campaign and Lore Panel (Full). Youtube. Accessed 2011-10-22.
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 StarCraft Legacy staff. 2011-05-30. May 2011 HoTS Gameplay Info. StarCraft Legacy. Accessed 2011-05-31.
  3. Heart of the Swarm Screenshots, Kotaku. Accessed on 2011-07-08
  4. 2011-21-10, Interview: Starcraft 2: Heart of the Swarm - Campaign and Lore Facts You Need To Know. G4TV, accessed on 2011-21-10
  5. Blizzard Entertainment. StarCraft II: Legacy of the Void Map Editor. (Activision Blizzard) (in English). March 12, 2013