"Last, but not least, is the spawner of the swarm: the Swarm Host. These guys can create numerous pesky locusts and now, we know how. So check out all the details, and arm yourself and those around you with an understanding of one of our greatest foes."
SwarmHost SC2-HotS Art2

A swarm host

The swarm host (otherwise known as the "egg monster" by terrans)[1] is a zerg strain in StarCraft II: Heart of the Swarm.


"Adapted using primal essence. Spawns locusts to kill enemies."
SwarmHost SC2-HotS Art1

A swarm host spawning locusts

Generated by the infestation pit, the swarm host burrows into the ground in order to provide a seemingly endless supply of locusts.[2] A single swarm host is capable of overwhelming an entire army.[3] The large, mushroom-shaped structure on the swarm host’s back is a breeding ground that weaponizes the millions of diminute larvae inhabiting the creature’s acidic bloodstream. Through a simple system of membranes for matter exchange, glands that pump the offspring full of hormones to hyper-accelerate growth, and ducts for efficient transportation to the bubbling pockets on the surface of the incubator, the swarm host births deadly, short-lived locusts to destroy threats to the Swarm. The larvae also feed on damaged tissue, sealing wounds, and destroying anything foreign that enters their domain. When the creature is threatened or engaged in combat, a subtle chemical reaction signals the larva to head for the incubator, where they are evolved into living weapons.[4]

SwarmHost SC-FM Art1

A swarm host

The swarm host is often used in defensive maneuvers.[2] Its legs boast powerful muscles that allow them to vibrate at hypersonic speeds, not unlike the teeth of the nydus worm. Despite that, the creature couldn´t burrow fast enough to adapt to shifting battlefield conditions. To correct this, a set of fragile (albeit regenerating) capillaries was put into place. Now, when the swarm host digs, the capillaries break and the creature’s acid blood softens the soil, allowing it to go underground in seconds. Flexible osseous structures of varying thickness slide and lock into position when the swarm host prepares to strike. Bearing a resemblance to siege tank hydraulics, this specialized skeletal system allows the swarm host to maintain position and balance when spewing locusts or when under heavy fire.[4] The swarm host lacks mobility however, which leaves it vulnerable to quicker enemies with area damage like the hellion.[2]

LeviathanSwarmHost SC2SkinImage

A Leviathan Brood swarm host

The swarm hosts of the Leviathan Brood are uniquely specialized for amphibious assault and bear many genetic advantages that allow them to quickly move through the oceans and assail their prey.[3]


The first swarm hosts encountered by the Swarm were primal zerg on Zerus, used against Kerrigan's forces by the pack leader Brakk.[5] Swarm host strains were incorporated into Kerrigan's Swarm soon afterwards by Abathur, adapted through primal essence.[6]

Recent reports within the Dominion have suggested that swarm hosts have developed the ability to spawn locusts without being burrowed.[1]

During the End War, a number of swarm hosts came under Amon's control, and were inducted into his brood. They were encountered by Tal'darim Highlord Alarak and Nerazim Matriarch Vorazun on Aiur. [7]

Game UnitEdit

The swarm host's Summon Locust ability changed dramatically in April 2015. The ability is now manually cast with the hotkey "C", and the cooldown increased to 60 seconds. It can be used whether the swarm host is burrowed or not.[8]

Swarm hosts cannot attack directly.


Many zerg ground units may burrow, become invisible and may be revealed primarily by detectors, and may not move or attack. Exceptions are the roach, which may move while burrowed, the infestor, which may move and cast Infested Terran,[9] and the baneling, which can detonate while burrowed.

Some units can unburrow via autocast, causing them to emerge and attack when an enemy moves into range.

The ability is not smartcast.

Hotkey R
Cost 2 seconds to burrow, 1 second to unburrowTime SC2 Game1
Purchased from Hatchery/Lair/Hive
Hotkey B
Cost 100 Minerals Terran SC1 100 Gas Terran SC1 71Time SC2 Game1
Required Lair (WoL)
Hatchery (HotS/LotV)


Flying Locusts

Allows locusts spawned by swarm hosts to fly. Flying locusts can use Swoop to land and attack units.

Automatically available in Legacy of the Void.

Purchased from

Infestation pit (HotS)

Already researched (LotV)
Hotkey L
Cost 200 Minerals Terran SC1 200 Gas Terran SC1 160Time SC2 Game1
  • +1 bonus to armor per level for zerg ground units.
Purchased from Evolution chamber
Hotkey C
Level 1
Cost 150 Minerals Terran SC1 150 Gas Terran SC1 114Time SC2 Game1
Level 2
Cost 225 Minerals Terran SC1 225 Gas Terran SC1 136Time SC2 Game1
Required Lair
Level 3
Cost 300 Minerals Terran SC1 300 Gas Terran SC1 157Time SC2 Game1
Required Hive

Heart of the SwarmEdit

EnduringLocusts SC2-HotS Icon
Enduring Locusts

Increases the lifespan of locusts by 10 seconds (to 25 seconds). This upgrade was removed from HotS in the April 2015 update, as the locust's base lifespan was increased to 25 seconds. [10]

This upgrade is not present in Legacy of the Void.[11]

Purchased from Infestation pit
Hotkey L
Cost 200 Minerals Terran SC1 200 Gas Terran SC1 120Time SC2 Game1

Heart of the Swarm CampaignEdit

Swarm hosts appear as primal zerg enemy units in "Waking the Ancient."[5] Afterwards, the player gains access to them in "The Crucible."[6] They have access to a number of upgrades in the evolution pit.[12]

In the campaign swarm hosts function differently. They do not burrow, instead using the root command. While rooted, a swarm host cannot move but is still visible. They do not autocast spawn locusts in the same way as in the multiplayer game. Instead, they only spawn locusts, while rooted, when an enemy comes into range, or the player selects spawn locusts and clicks a location.


SwarmHost SC2-HotS Story1

The swarm host upgrade screen


Allows swarm host to burrow. Can still spawn locusts while burrowed.

Primal sequences of swarm host resistant to improvement. Frustrating. Simple adaptations become incredible challenge. Essence constantly adapting, rejecting mutations. Aggravating. Difficult, but can enable burrow. Locust spawning will remain functional while submerged.

Campaign Acquisition
SC2 RapidIncubation Icon
Rapid Incubation

Locusts spawn 20% faster.

Locust production inefficient. Will greatly benefit from redundancy removal. Sequences are complex, wasteful. Byproduct of wild, uncontrolled evolution. Simplification of sequences will allow swarm hosts to incubate full-grown locusts at rapid speeds.

Campaign Acquisition
SC2 PressurizedGlands Icon
Pressurized Glands

Locusts can attack both ground and air units.

Swarm host defense reliant on locust organism. Locust secrets solvent fluids, projectiles towards enemy. Can mutate glands, increase pressure. Will allow projectile to reach incredible height. Attack both ground and aerial targets.

Campaign Acquisition

Legacy of the VoidEdit

In Legacy of the Void, swarm hosts can produce locusts on the move;[13] this ability is now manually activated.[14] These locusts are more powerful but do not spawn as quickly. In the late game the locusts can fly[13] over terrain. The locusts must then "swoop" to attack.[14]

Swarm hosts now require the burrow ability to be researched for them. They no longer collide with locusts.[15] They can no longer move while burrowed.[16]

Co-op MissionsEdit

Abathur is able to mutate swarm hosts in Co-op Missions. He is able to upgrade them when he reaches Level 9.


DeepTunnel SC2 Icon1
Deep Tunnel

Swarm host can burrow to any visible location on the map.

Hotkey D
Cost 2Time SC2 Game1
Campaign Acquisition
Unlock Reach Abathur Level 9
Purchased from Infestation pit
Hotkey D
Cost 200 Minerals Terran SC1 200 ZergVespene SC2 Game1 120Time SC2 Game1


SC2 PressurizedGlands Icon
Pressurized Glands

Locusts can attack both air and ground units.

Campaign Acquisition
Unlock Initially available
Purchased from Infestation pit
Hotkey P
Cost 200 Minerals Terran SC1 200 ZergVespene SC2 Game1 120Time SC2 Game1


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

Infestor SC2 Cncpt1

Swarm hosts development image

Main article: Infestor/Development

The swarm host[17] was expected to be available in the campaign and map editor of StarCraft II.[18] As the swarm host is now, it could have been an aerial unit, but it eventually became a ground one.[19] The idea behind its current design was to give zerg players their own siege unit, but make sure it functioned in a different manner to the siege tank or colossus.[20]

The swarm host's current form was to give the zerg a new aesthetic, something to distinguish the unit from the usual claws and teeth that other zerg units possess.[21]

"Egg monster" and "digester" are terms used for the swarm host in the beta files of Heart of the Swarm.[22]

Heroes of the StormEdit

Heroes DevLog2

The following section contains information from Heroes of the Storm and is not canon to StarCraft continuity

Swarm hosts appear as a boss mercenary on the Warhead Junction map of Heroes of the Storm.[23]

Variant StrainsEdit



  1. 1.0 1.1 2015-09-18, NYCC 2015 – James Waugh’s StarCraft Field Manual Signing Schedule. Blizzplanet, accessed on 2015-09-23
  2. 2.0 2.1 2.2 Swarm Host, Blizzard Entertainment. Accessed on 2014-01-08
  3. 3.0 3.1 Blizzard Entertainment. StarCraft II: Legacy of the Void. Collections Tab: Skins. July 19, 2017
  4. 4.0 4.1 2014-12-04, Swarm Host Science. Blizzard Entertainment, accessed on 2014-12-06
  5. 5.0 5.1 Blizzard Entertainment. StarCraft II: Heart of the Swarm. (Activision Blizzard). PC. Mission: Heart of the Swarm, Waking the Ancient (in English). 2013-03-12.
  6. 6.0 6.1 Blizzard Entertainment. StarCraft II: Heart of the Swarm. (Activision Blizzard). PC. Mission: Heart of the Swarm, The Crucible (in English). 2013-03-12.
  7. Blizzard Entertainment. StarCraft II: Legacy of the Void. Mission: Templar's Return. (in English). November 10, 2015
  8. Blizzard Entertainment. 2015-04-07. Heart of the Swarm Balance Update -- April 9, 2015. Blizzard Entertainment. Accessed 2015-05-11.
  9. Blizzard Entertainment Staff. 2010-07-24. Infestor. Blizzard Entertainment. Accessed 2010-07-24.
  10. Blizzard Entertainment. 2015-04-07. Heart of the Swarm Balance Update -- April 9, 2015. Blizzard Entertainment. Accessed 2015-05-11.
  11. 2015-03-31, StarCraft II Legacy of the Void Beta Release Patch Notes. Blizzard Entertainment, accessed on 2015-04-03
  12. Blizzard Entertainment. StarCraft II: Heart of the Swarm. (Activision Blizzard). PC. Evolution pit units (in English). 2013.
  13. 13.0 13.1 Blizzard Entertainment. 2014-11-07. Legacy of the Void - Multiplayer Update: Zerg. Blizzard Entertainment. Accessed 2014-11-09.
  14. 14.0 14.1 Blizzard Entertainment. 2014-11-08. Legacy of the Void: Multiplayer Preview. Blizzard Entertainment. Accessed 2014-11-09.
  15. Cite error: Invalid <ref> tag; no text was provided for refs named BetaPatch
  16. Blizzard Entertainment. 2015-05-21. Legacy of the Void Beta: Balance Update Preview - May 21. Blizzard Entertainment. Accessed 2015-05-22.
  17. 2010-02-28, StarCraft II Beta Game Images. StarCraft Legacy. Accessed on 2010-06-22
  18. Didier, Samwise, PC Gamer staff. "Alien Makeover: Blizzard shows off the new look of the zerg." PC Gamer June 2009: 20-22.
  19. 2011-10-23, BlizzCon 2011 - Starcraft 2: Heart of the Swarm and Blizzard DOTA - Art & Technology Panel (Full). YouTube, accessed on 2011-11-07
  20. June, 2012, Starcraft 2: Heart of the Swarm "New Units" Explained by David Kim. G4, accessed on 2012-06-21
  21. June, 2012, Starcraft 2: Heart of the Swarm "New Units" Gameplay Preview With Sam Didier. G4, accessed on 2012-06-21
  22. Blizzard Entertainment. Heart of the Swarm beta Map Editor. (Activision Blizzard) (in English). September 4, 2012
  23. Blizzard Entertainment. Heroes of the Storm (Blizzard Entertainment) (in English). June 2, 2015