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Gonarch model.jpg
General information

Xen wildlife


Headcrab breeder

Personal information


  • Hazardous chemicals
  • Front legs
  • Spawn baby Headcrabs
Game information



The Gonarch is the final life phase of the Headcrab[1] introduced in Half-Life. It is encountered on Xen in the chapter Gonarch's Lair, acting as a boss.


The Gonarch "shooting" its harmful chemicals.

The Gonarch's body is composed of a smooth dark brown carapace, supported by four arthropod-like legs, and a large fleshy and gelatinous egg sac that dangles from its underbelly. Little is known about how and when the metamorphosis from a Headcrab to a Gonarch takes place, as few Headcrabs ever reach this stage.[1]

Behavior and skills[edit]

Baby Headcrab.

The Gonarch is almost completely invulnerable to damage, with the large sac that hangs below the thorax being its only vulnerable area. From afar, the creature spews out white globs of harmful chemicals from the top of its carapace to "shoot" at its attacker, itself being immune to acid.[3] At close range, it uses its front legs to swipe at its foe, dealing massive amounts of damage. These attacks can harm and kill any other enemies within range.

When in sight of an intruder, the Gonarch rapidly reproduces baby Headcrabs in large numbers from its sac, birthing them in pairs.[3] The babies are not very dangerous on their own but can swarm at attackers in groups, distracting them from their breeder. If any young Headcrabs are killed, the creature continuously spawns more to take their place; at any given moment, there can be up to 20 live baby Headcrabs.[3]

When it spots the player, melee attacks, takes damage, and dies, the Gonarch produces loud whining cries. It emits low-pitched mournful sounds when a baby Headcrab is killed. Upon death, the Gonarch destructively explodes, destroying any frangible structures in its vicinity and releasing a large number of offspring. Its explosion, however, does not harm the player or other nearby enemies.

Interestingly, despite its massive size, the Gonarch is capable of walking and running on webbing that covers up pits in two areas of its lair with ease, whereas both the player and other enemies simply fall through them. Of note is also its relationship with Xen Trees, as it is never attacked by them.[4]

Behind the scenes[edit]

As stated by Gabe Newell, the Gonarch was created when someone at Valve asked, "Why don't we put a giant testicle on a 20-foot-tall armored spider?"; its gameplay purpose was fit to this design. Strong art direction and clear goals were set for the creature from the start, but the AI proved to be very complicated due to its size and how different it was from the more common game monsters of that time.[1]

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 fact Backman did not agree with. However, Gabe Newell liked it, which greatly influenced its inclusion in the game.[1] The creature's design seen in early concept art survived the development of the game without major changes. The Gonarch was nicknamed the "Big Momma" or "Big Mama" by Valve.[1] This name can be seen in the game files, with the creature's model and entity being called big_mom.mdl and monster_bigmomma respectively. Its final "Gonarch" name is composed of two combining forms. The definition of the "gon-" prefix refers to the male reproductive organ, and the "-arch" suffix means leader.

The Gonarch uses custom info_bigmomma nodes to navigate and can only be damaged during certain sequences. When it arrives at its destination, it engages in combat with the player until it takes enough damage for the next node to be activated.

Some animations were not fully implemented. Unused defend animation, identical to the jump and angry1 animations, shows the Gonarch taking a guarding stance; of note is its assigned ACT_GUARD activity, one that can be seen employed in Houndeyes. As the Gonarch is scripted to play the longer falldeath animation upon death, the standard death animation cannot be seen in-game. fall1 and fall2, meant to be used during the creatures's descend into the cavern, remain unused as well, being replaced in the final game with jump.

In the early stages of Half-Life 2's development, a device used to spawn Headcrabs from a Gonarch's sack, the "Combine Big Momma Pod", was to be seen in Ravenholm.[5][6]


List of appearances[edit]

Main games[edit]