Headcrab
Headcrabs (Capitus Nepocaris), native to Costa Bravo, are strange, almost alien creatures, seen as common pests by the residents of Costa Bravo. The central, most common subspecies of Headcrab has mottled tan-colored skin and reddish legs, and consists of a small rounded body with four legs for movement (two stubby legs at the front, obscured by its claws, and two hind legs at the back) and a pair of frontal claws for attacking prey or additional support when standing still.
Behavior
Although small, slow-moving, and relatively weak on its own, the headcrab has the ability to quickly leap long distances using its hind legs, while tilting upwards to face its mouth towards its target, inflicting minor injury with its claws, legs, and teeth. Its primary goal, however, is to attach itself onto an appropriate host body.
Headcrabs have a penchant to lie in wait in dark corners and ventilation shafts. In more open environments, headcrabs are known to bury themselves in the ground to hide, undetected, then climb out to the surface and attack when a victim draws near. Headcrabs are often seen in groups, though they lack any sort of traditional hierarchy seen in other species. They will pursue their prey under the most dangerous conditions, moving through dangerous areas or towards hostile prey with little concern for the consequences, even as their fellow headcrabs die in front of them.
Headcrabs can produce a variety of vocalisations. When they are not hunting, headcrabs usually emit squeaks and fairly quiet, repetitive calls, whilst gently swaying their bodies back and forth. When attacking, the headcrab will emit a sharp, shrill shriek as it leaps towards its victim.
Headcrab Zombie
A headcrab's primary goal is to attach to the head of a suitable host using its mouth, and burrow its claws and hind legs into the head or upper torso, whereupon it takes control over its victim's body, rendering him a mindless zombie-like being. The headcrab's parasitic ability is also speculated to be similar by the capability of the Emerald Cockroach Wasp to paralyze and control "zombie" cockroaches, in a manner that could be similar to how a headcrab controls its host.
Interestingly, no species other than humans have been observed infested with headcrabs. Indeed, the physical makeup of the headcrab, and its apparent need to clamp on the "head" of a humanoid makes it unlikely that it is capable of "zombifying" other creatures. As such, the diet of headcrabs is not principally taken from the "zombification" of their hosts, but rather through standard means.
Standard Headcrab Zombie
When a headcrab successfully attaches to a host, the host becomes a "headcrab zombie", or, formally a "necrotic". The headcrab secretes a strange serum into their host's bloodstream, which causes various "mutations" to rapidly manifest in its host, such as elongated claws, increased strength, and a sharp-toothed, sideways mouth that bisects the victim's chest cavity from neck to groin. This giant mouth has inspired the nickname "Mawmen". Necrotics do not appear to retain any of their former intelligence, blindly pursuing their prey, oblivious to danger. Occasionally, a small number of necrotics survive for quite some time, despite losing both legs and its lower torso, by crawling and moving using its arms. As such, it is presumed that headcrabs secrete a sort of intense coagulant into their host's bloodstream as well, to prevent their bleeding to death.
In most cases, a headcrab remains attached to its host until destroyed, although occasionally they detach from the host if it is damaged significantly. Removal of the headcrab reveals that the host's face and head has been eaten away by the creature; the degree of such damage on these areas depends on the type of headcrab in control. Horrified sounds emanating from necrotics imply that, while severely wounded, the host creature is at least partially aware of its horrific situation. Necrotics often produce extremely disturbing and guttural yells of pain.
