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The Gonarch is the final phase of the Headcrab's life-cycle.[1] It is encountered in a boss battle taking place in one of the last chapters of Half-Life, Gonarch's Lair. Only a single Gonarch is encountered by Gordon Freeman during the game. This is a female headcrab.


Little is known about how and when the metamorphosis from Headcrab to Gonarch takes place, as few Headcrabs ever reach that stage.[1] The Gonarch boasts a thick exoskeleton, powerful legs, and a large sack resembling a testicle dangling from its underbelly. It can easily withstand massive amounts of projectile and explosive damage, taking even more explosive damage to kill than a Gargantua.

Headcrab baby

Baby Headcrab model.

The large bag of flesh which hangs from the creature, commonly referred to as its "sack", seems to be a reproductive housing. During the battle with Gordon, it releases undeveloped baby Headcrabs at a rapid rate with no apparent limit to their quantity. Small and soft-looking, these Baby Headcrabs are not very dangerous, but they can walk a bit faster than full-grown Headcrabs, attack rapidly and are smaller (almost a third of a full grown Headcrab) and thus more difficult to hit. The Gonarch makes loud, mournful-like sounds when a Baby Headcrab is killed. When the Gonarch is angry or injured, it will emit a loud cry.

The Gonarch seems to lack sensory organs. However, during the attack on Gordon, the Gonarch never comes close to running off the edge of its platform.

Entering the Gonarch's lair results in an immediate attack. Gonarchs attack by charging at their victim, then attempting to puncture them with their massive legs. They also have a ranged attack: yellowish balls of acidic material from the top of their shells which they hurl through the air like mortars, raining down upon the victim. After taking a certain amount of damage, the Gonarch will flee, and Freeman has to pursue it through the level. Upon death, the Gonarch explodes violently.

Behind the scenes[]

Gonarch concept

Concept art.

  • The creature was originally known under the nickname "Big Momma".[1] Its model is also named "big_mom.mdl", while its entity is "monster_bigmomma".
  • The Gonarch was apparently born very simply, when someone at Valve asked, according to Gabe Newell, "Why don't we put a giant testicle on a 20-foot-tall armored spider?".[1] Therefore the name may be a portmanteau of the words "gonad" and "monarch". A "gonad" is a scientific term for the reproductive organ of any living creature, the male mammalian gonad being the testicles. The "monarch" part would refer to the creature's hierarchical status in the headcrab’s lifecycle, or simply its "boss" status within the game.
  • According to Ted Backman, the Gonarch was a strongly contested design around Valve's office during the development of Half-Life, considered by some to be too graphic, a thing Backman did not agree with. However Gabe Newell liked it, which greatly influenced its inclusion in the game.[1]
  • Strong art direction and clear goals were set for the Gonarch from the start, but the AI proved to be very complicated due to the size of the creature and how different it was from the more common game monsters of that time.[1]


  • The Gonarch appears to be very weak if spawned directly through the console using commands, and usually ends up dying after being hit with a single magazine of the Glock pistol ammo, and will not explode after death. However, in Half-Life: Source, the console-spawned Gonarch is invincible.




List of appearances[]