Gonarch

A Gonarch is a fictional creature in the 1998 first-person shooter computer game Half-Life. Only a single Gonarch is encountered by Gordon Freeman during the game. It is located within a chapter named "Gonarch's Lair" set in the border world Xen and acts as a boss in a protracted battle that takes place in the closing stages of the game.

Description
Very little is known about a Gonarch's life cycle. What is known is that a Gonarch is the last stage of a female headcrab's life and that like most Terran non-human organism with a high mortality rate, very few female headcrabs reach this stage. While appearing very similar to a headcrab's anatomy there are a few differences. Gonarchs are supported by four razor sharp limbs. Standing at several meters tall, they dominate Gordon in size and power. Gonarchs are easily one of the largest and toughest known creatures from Xen. Heavily armored with an exoskeleton, they can take massive amounts of projectile and explosive damage, taking even more explosive damage to kill than a Gargantua. Because of this heavy armoring it is usually best to concentrate fire on the only unarmored part of a Gonarch, which is the large soft sac that hangs from the underside of the creature.

The large bag of flesh which hangs from the creature, commonly referred to as its "sac," seems to be a reproductive housing. During the battle with Gordon, it releases underdeveloped baby headcrabs at a rapid rate. These baby headcrabs, while mostly harmless, can be greatly troublesome en masse. Nothing is currently known about how Gonarchs reproduce. While Gonarchs appear to be mindless breeding machines, there is some evidence that they can feel emotion of some kind. When one of its offspring is killed, it will make an unusual and sad-sounding cry, suggesting it mourns for its dead young. Gonarchs are known to make other noises as well--most notably, when they are angry or injured, they will emit a loud cry, very similar to that of an elephant.

Entering a Gonarch's lair results in immediate attack, suggesting that they are highly territorial creatures, that they are highly protective of their young, or both. They attack by charging at their victim, then attempting to puncture them with their massive legs. They also have something of a ranged attack, by forcing yellowish balls of acidic material from the top of their shells, which they hurl through the air like mortars, raining down upon the victim. With all their traits combined, Gonarchs prove to be skilled at defending themselves and their young, and are one of the toughest enemies Gordon faces in Xen. Upon death, a Gonarch explodes violently.

Name
Within Valve Software, the creature is known as "Big Momma" (cf. its model name, ), a name that was given to it early on by staff developing Half-Life. Regarding the species name, one theory is that it is a portmanteau of the words "gonad" and "monarch." "Gonad" stems from the resemblance of the large sac that hangs beneath the Gonarch to a scrotum, while "monarch" references the Gonarch's role as a "king" enemy. This theory is supported by the book Half-Life 2: Raising the Bar, in which the following appears:

Half-Life 2
While the Gonarch is not encountered in Half-Life 2, an amputated part of it exists as an unused model a file in the leak version of Half-Life 2. This amputated part, essentially nothing but the sac that hangs beneath the Gonarch's body, is covered by many metallic supports (see here). It is likely that this model was created to explain how the Combine produce large quantities of headcrabs for use as weaponry. This fusion of living material with technology is entirely in keeping with the Combine forces that are encountered in Half-Life 2.