Hailing from the borderworld of Xen, the creatures known as "Head-Crabs," scientifically referred to as Craniumparasitus, exhibit intriguing characteristics unlike anything of earthly origin. Headcrabs are nest-borne organisms, their eggs hidden within these nests, making them exceedingly challenging to locate even if the nest is found. What sets them apart is their asexual mode of reproduction, lacking the need for distinct male and female counterparts.
Headcrabs bereft of a suitable host gradually develop a Nosos Heart within their bodies, rendering them incapable of latching onto hosts. Instead, they roam their territory in search of a suitable nesting site to begin the next generation. These creatures are notorious for their lowly position on the food chain and rarely partake in predation unless a fortunate encounter with a host presents itself. Numerous xenian predators, such as bullsquids, consider them a source of food.
One inherent vulnerability of the Headcrab lies in its rigid biological limitations; it can only infest humanoid hosts. This constraint further contributes to their marginalized position within their previous ecosystem of Xen.
The Headcrab Life Cycle
By Kranky
Baby Headcrabs
The first stage in any headcrab's life is that of a baby headcrab, being unable to latch onto a being's head and is merely growing from its nest - Or in some rarer cases in the modern time from a Gonarch. These headcrabs will undergo 1-2 weeks of growing until they are a full adult - Where they will either burrow into the ground to wait for prey or wander the wastes to find a host.
Approximately after half a week after hatching the baby-headcrab will separate from its nest, going off into finding a suitable place to burrow as they mature. Baby-Headcrabs will not attack beings larger than itself unless it has no other choice.
Adult headcrabs
Since the combine's rule on earth began there are three types of adult headcrabs. Two of which have been genetically modified to become a weapon for the combine's utility. Though however they all start as baby headcrabs.
Poison Headcrab  A highly dangerous foe biologically engineered by the combine to be used as weapons, instead of using its claws to attach to a host it will first use venom within multiple fangs within their beaks. Of which they use to incapacitate their prey and then they will begin the hosting process. These are rather uncommon, and have rarely been seen used by the combine as a weapon - Usually used as a last resort for if major attacks do fail. Upon gathering a host multiple eggs will be spread about the host's body, forming the well-feared poison zombie. These zombies will tend to throw the excess poison headcrabs from its back, allowing it to have a ranged attack. | Standard Adult Headcrab  The most common varient of Headcrab on the planet, being the organic matured adult of the baby-headcrab these are commonly found burrowed in the dirt or travelling in groups. Noticable features of these headcrabs is the development of their beak and talons - Allowing them to now latch onto prey much larger than them to become their host. In very rare circumstances if a standard adult headcrab manages to live for months on end they will become an 'alpha headcrab', becoming much larger and significantly more powerful than its smaller counterpart - Though loses its ability to couple with a host. | Fast Headcrab  The fast headcrab is another biologically engineered headcrab, being evidently by the name much faster than the standard headcrab. They have exchanged their claws and other attachment spikes on their form in trade for becoming a much faster and more dangerous foe. Instead of only having two talons they sport four thin talons. Typically they will disable their prey before coupling with the host, taking one to two weeks to fully take over the host's body and mutate it into the well known fast zombie. Fast zombies tend to roam in groups of 4-5, commonly called "Hunts" of fast zombies. In rare cases do multiple hunts form together to form a massive hunt of 20-25 fast zombies. |
Standard head-crab mutation tree
S-01 "Zombie"
Stage one of the headcrab's host mutation process sees the host losing flesh around their hands, creating claws - and their torso being ripped open exposing the organs inside. The torso is used as its feeding point, being able to intake any form of meat - This is the most common stage that head-crabs die in due to their slow pace and lack of good vision. They typically wander in groups however many tend to roam alone.
S-02 "Large Zombie/Mutant"
Stage two zombies tend to see much further mutations within their host's body, now turning the ribs into full on teeth - and turning the flesh around such into a functional mouth. This tends to take 1-2 weeks after initial coupling with the host. These zombies are more importantly much smarter and have better vision than that of the standard zombie, roaming in groups of four. They can see a variety of extra mutations along with this - being able to run on occasions or their size changing significantly.
S-03 "Gonomes"  The final stage of any head-crab is after one month after the initial coupling. Mutating much more randomly here as now they are larger - more powerful - and much smarter than the standard zombie. The Gonome also has an extremely useful weapon at its disposal - Heavily Coagulated blood that forms at the mouth of the beast that may be used to throw at threats it battles. Along with this Gonomes tend to run to chase their prey down, and are commonly found making 'nests' for more headcrabs to begin their own life-cycle. |
Rare Occurances
Gonarchs
A rare version of the head-crab that acts as a walking nest is the Gonarch, standing at incredible heights the Gonarch is an extremely capable foe. It is a side effect of the ever-so-rare "Alpha Headcrab", as alpha headcrabs can no longer couple with the head of a host - Merely utilizing their extremely strong attacks.
Armored Headcrabs
Armored headcrabs are the combination of a headcrab and a larger xenian infestation - It is a rare occurrence as only a certain xenian growth type may be able to create these head-crabs. They have a dense layer of hardened chitin able to withstand most standard weapon calibers- However they have a weakness where their beak lays.
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