A Nomad Incubus is a special type of Nomad creature designed specifically to be implanted in a human host, called an Infectee afterward. These Nomad Agents were the main deployed force of the Nomads during the Nomad War, and are the foundation of the Wild's covert operations. Without them, the Nomads would be unable to hide amongst humans, and would thus be far less threatening.
When the Nomads were awakened around 350 A.S., they largely avoided humanity, lacking a basic understanding of almost every aspect of them, from biology, to culture, to their basic human nature. Eventually, seeing the looming threat of discovery, the Nomads took it upon themselves to study and understand their potential enemies. Human pilots gone missing in the deep Omicrons were sometimes subjects of the Nomads experiments, and eventually, they discovered that they might be able to manipulate or even control humans, either with telepathy or more direct methods. By turning parts of humanity against itself, their greatest obstacles could become their greatest strengths.
The earliest of the newly formed "Infiltrator" caste were existing Nomad bodies crudely merged onto humans, more akin to modern hybrids than infested humans. However, with further experimentation and engineering, the Nomads developed a new demi-organism which could be stored compactly and unfold when placed in a host, preventing passerby from detecting that anything was amiss. The resulting creatures, known as Nomad Incubi, an offshoot of the Nomads, were parasites capable of dominating and controlling a human host. Mind and body, their primary purpose was to integrate into humans.
"Infestation" covers everything from initial implantation to the manifestation of 'telekinetic' abilities. While it takes less than a fortnight for an Incubus to control its host, it continues expanding and developing for much longer. As Incubi are relatively new creatures, their lifespan is unknown- as of yet, no evidence exists to suggest that an Incubus will expire before its host.
Incubi are constructed as seeds, containing only the bare minimum needed to take root in a human host. While in seed form, they can be transported across the stars easily, and remain dormant until implanted in a host. Mature Incubi can also manufacture seeds of their own, which they can then spread to new hosts orally.
When implanted in a host, either by surgery or by oral delivery from another Incubus, an Incubus seed makes its way to the human's spine; if delivered orally, they must tunnel through the stomach walls to do so, resulting in the characteristic period of sickness experienced by newly infested. From the spine, they begin to unpack and expand along the nervous system, taking root at the base of the brain stem. The growing Incubus will put itself between the brain stem and the spine, severing direct connection and forcing all electrical impulses from the brain to pass through it before continuing on to the body. As the Incubus acclimates to its specific host, it will begin to exercise its control, testing itself and learning how to operate its body. During this period, the human is still able to perform normal bodily functions, as the Incubus is capable of letting human commands reach the rest of the body. Within a week or two, depending on the host, the Incubus will be able to exert full control over the host, though it will not be able to manifest many of the abilities infectees are capable of.
As the Incubus continues to grow, it draws upon the host's metabolism to feed its development. The host may maintain a ravenous appetite, similar to the effects of a tapeworm. This energy is used to expand the base creature along the muscles of the host, enabling faster and more efficient control of the host's body. By exerting energy across the farther parts of its body, the Incubus may even augment the base physical prowess of its host, the effect becoming more dramatic as time progresses. Further along, the Incubus may be able to push its body beyond the boundaries of the host, putting forth nearly invisible tendrils through the host's skin. While at first these serve only as extended senses, with a powerful enough host and a significant supply of energy, they may be used to exert force upon outside objects, best known as 'telekinesis'.
Being relatively new creatures, the lifespan on an Incubus is unknown. So long as they have a host to sustain them, an Incubus might theoretically survive indefinitely; only time will tell whether Incubi can age to death.