Shadow

Shadow (影 (シャドー), Kage) are a sub-type of Hollow that are born when the encroachment process on a Plus is interrupted, leaving them in a Demi-Hollow like state. They began to appear after the Winter War, and unlike normal Hollows, which devour souls, they act as a virus and a parasite, driven by the instinct to infect and spread themselves. Shadows are thought to originate from the Human World, though it is still unknown how they were created.

Overview
Shadows are former Demi-Hollows that, instead of fully hollowfying via the normal process, are stuck in a state somewhere between a Hollow and a Plus. They are different from normal Hollows in that they operate akin to a virus and a parasite.

Transformation Process
A Human soul becomes a Shadow by the same basic prcess one becomes a Hollow. As a deceased person's chain of fate degrades, they undergo hollowfication. However, a Shadow is born when something stops the chain of fate from degrading all the way, leaving the festering end of the chain hanging from an incomplete hollow hole. This only works if the original hollowification had gotten to the point that a hollow hole had opened and the person had become a Demi-Hollow. With the process nearly complete, but frozen, a Demi-Hollow's body and mind will start to degrade from the pain. Their skin will thicken and lose color, their hair will fall out, their muscles and fat are consumed to next to nothing, and they lose any distinguishing features, leaving nothing but a husk of a soul.

Only Human souls with no outstanding spiritual pressure can become a shadow. Weak Hollows have also been observed to turn into normal shadows by having an infected chain of fate inserted into its hollow hole.
 * Spread: Although the original source of the Shadows is unknown, it is known that a normal Shadow change a Plus by biting off the Plus's chain of fate. The bite snaps the chain but also prevents it from eroding further, transforming that soul into a Shadow much more quickly than the normal hollowfication. The attacking Shadow will collect the severed chain of fate and 'insert' it through its own incomplete hollow hole. This behavior is discussed below.

Behavior
Shadows are similar to Hollows in that their only goal is to seek out other souls to devour. However, instead of eating them Shadows seek to infect and spread themselves, much like a virus. They are driven by a hive-mind like force to find and infect other souls, and are aggressive and unrelenting in their pursuits. Shadows, in their most basic form, are seemingly mindless. They cannot speak or interact with other things outside of infecting them. However, as a Shadow collects trophy chains it absorbs more spiritual pressure, making it stronger and more intelligent.  Shadows operate in a mob mentality, just like ants. They are rarely seen alone, and tend to aggregate and follow other shadows. Groups do not have a size limit, which is the very trait that makes them so dangerous.

Shadows cannot infect dead soul bodies, and will instead consume the soul body before it has a chance to reincarnate, completely eradicating it.

At their intelligence threshold, a shadow can gain the ability so speak and think more tactically. However, the basal instinct of spreading their infection is still the driving force behind a shadow's behavior.

Appearance
All shadows appear as thin, hairless humanoids. They are essentially skeletons with a thick layer of red-tinged, dark grey skin stretched tightly over the bones. They appear to have little to no muscle and no fat, instead their bones stick out prominently under the skin. Their hands and feet end in pointed, short claws, and All shadows lack any reproductive organs and do not have sex-identifying features. In fact, all shadows are nearly identical except for height.
 * Mask:  Most striking is a shadow's mask. They are all the same, and appear as a stylized version of the front section of a human skull, complete with a fully articulate jaw and exposed teeth. The masks have no eye sockets, nasal passages or fenestrae, and only cover the front of a shadow's 'face', exposing the small lumps of flesh that were once their ears. All shadow masks are identical.
 * Chain of Fate and Hollow Hole:  A final distinguishing feature is a shadow's incomplete hollow hole and severed chain of fate. The hole itself is not actually complete- there is a thin membrane of flesh in the center of the hole that the chain, and 'trophy' chains attach to. Generally a severed chain reaches no longer than three feet. Different shadows possess different numbers of trophy chains, depending on how many souls they have corrupted, Each new chain is worn through the hole and slung over a shadow's shoulder like a shirt strap or hanging over the ribs around to the back, connecting back into the hole through the shadow's back. With enough chains a shadow will have an 'x' across its chest and back.

Abilities
Individually, Shadows are rather weak creatures. However, they have several natural powers that aid in their spread. Shadows also have little to no discernable spiritual presence, making them incredibly hard to detect.
 * Soul-Body Separaton:  Shadows posses the ability to separate human souls from their living bodies. It appears that their skin itself facilitates this ability, as they have been seen pushing, yanking, and tackling souls out of bodies. If a human walks through a Shadow, their soul is pushed out of their body, chain of fate still attached.
 * Encroachment Interruption:  A Shadow's saliva contains a factor that halts the degradation of a plus's chain of fate. Instead of healing the chain, however, the last link is left to fester, causing excruciating pain and further soul corruption. The saliva also contains an infecting factor that aids in the process of shadow transformation, and is the main cause of hair, muscle, and fat loss.


 * Shadow Concealment:  This is the ability that coined the shadow's name: They posses the ability to flatten their spiritual presence into shadows and can move disguised like that. Though they cannot 'jump' shadows that aren't connected, they can travel through shaded areas. They also cannot completely hide themselves, and if someone looks closely they can see the shaded area moving strangely.


 * Soul Disguise:  A Shadow with enough chains to speak will also hold the ability to camouflage their appearance to any of the humans whose chains it has taken. This is not common; most shadows do not last long enough to gain this ability.

Soul Infection
The most worrisome ability in a Shadow's arsenal is its ability to enter a being with strong reiatsu's spiritual body. Hollows, Shinigami, Arrancar, Quincy, and Vizards are all susceptible to infection. Shadows enter a soul via hollow hole or saketsu, and once inside they can be removed with a soul-separating device (such as Rukia's glove). The only known way to resist infection is to kill the shadows trying to get in or not have a hollow hole or saketsu. Shadow cannot re-animate dead bodies. Infected souls are simply victims, however completely taken-over souls are known as hosts.
 * ​Process: Shadows infect their victims by condensing themselves and entering the chosen soul via a hollow hole or Saketsu. Numerous Shadows can enter a soul all at once, overwhelming them. Rate of infection depends on several factors: the spiritual pressure of the victim, the number of Shadows residing inside the victim, and the length of time a shadow has been inside a soul. For a weaker soul, infection happens rapidly and can occur with a small number of Shadows. However, a strong soul can actually destroy a single infecting Shadow if it is left alone, and many Shadows are needed to turn them into a host. It was recorded that Genryūsai Yamamoto, as a host, was carrying over fifty Shadows before he began to show signs of infection.
 * Shadows do not die with their host. When and if their host is slain, they will be expelled from the body relatively unharmed and ready to infect another. However, if expelled from their host by other means, a shadow will come out disoriented and easy to pick off.

At its worst the infection will force the victim to become cruel, merciless, and aggressive, and will turn them into sociopathic killing machines. Infected want to incapacitate or kill others in order to remove threats or make new hosts for other Shadows. They also will consume deceased spiritual beings, no matter the species. Completely infected beings are called hosts, and have no control over their actions. They will taunt and say cruel things to non-infected beings, however. They also do not feel pain or get tired, and will literally keep fighting until they fall apart or have the shadows removed.
 * Symptoms:  The initial symptoms of a shadow infection are similar to those of rabies: increased aggressiveness, paranoia, hallucinations, insomnia, anxiety, and abnormally angry or violent behavior. As the infection wears on the victim will experience a loss of feeling, and a degradation of personality, empathy, and will exhibit sociopathic behavior.
 * Physical symptoms start as a black, thick scab-like wound at the point of the first shadow's entry. This mark is a scar, and with it a victim is more easily entered by other shadows, even when the first infection has been removed. As the infection progresses the victim will begin to show black, raised vein-like marks on the surface of their skin, radiating from the infection's origin.
 * When a victim is completely taken over, their eyes will become completely black except for a thin white ring where their iris should be.
 * Physical Effects:  A Shadow infection, besides leaving a black scar at point of infection, is physically very harmful. Besides corrupting a victim's mind, infection also causes severe internal damage if left unchecked. If left too long, a victim's internal organs will begin to shut down, and once dead the infecting Shadows will be expelled from the body and they will consume it.
 * Hollow Masks: When a Hollow or Vizard is infected, their masks will lose all markings and turn plain white. Though a Hollow's mask will retain its shape, a Vizard's mask will lose distinguishing features (besides things like horns), will lose the eye sockets, and will change to look like a Shadow mask. A freed Vizard's mask will permanently be changed to appear like a Shadow's mask.
 * Treatment:  If caught and removed early, a Shadow infection will only affect a victim by leaving a permanent scar. However, if a victim has already started to undergo the symptoms of infection they will need immediate medical attention once the shadows are removed. Removal is a very painful, if quick, process, and drains the host's spiritual pressure, 'injuring' their reiatsu capability. A victim will also have moderate to severe internal injuries, and have internal bleeding or organ failure in some cases. If their internal injuries can be fixed, there are no other lasting physical affects besides them being more susceptible to later infection due to having traces of the expelled Shadows in their Reiyoku.
 * Mentally, a freshly freed victim will take some time to recover, depending on how degraded their mind had become. Personality has been seen to be fully recoverable. However, most victims remember what they did while infected, and many experience severe guilt, depression, and PTSD.

Infected Abilities

 * General: In general, a host's natural physical abilities remain the same as they were before infection. The only difference is a host develops a type of CIPA, and do not feel pain, fatigue, hunger, or any other physical ailment. Hosts are known to fight until their bodies literally fall apart, and are unaffected by injuries or the need to sleep or eat. Hosts also retain their instinctual fighting capabilities and habits, so the more experienced a host was before infection, the more dangerous they are. If many Shadow are inhabiting a host, they can access the host's memories and learned techniques.
 * Shinigami: A host Shinigami is unable to, in most cases, use kido because the shadows infecting them don't know how to access and shape their host's reiyoku. This also hinders their ability to use hoho. However, host Shinigami have been observed attempting to use their reiyoku, which often leads to large, uncontrolled bursts of reiatsu. A host also cannot access their Shikai or Bankai, as the Zanpakuto, in general, resists infection and will not listen to the commands of the Shadow-controlled host. Again, hosts have been witnessed attempting to access their Shikai, only to have the zanpakuto rebel and attempt to injure the host instead.
 * Visored: Similar to Shinigami, the only difference is, as a sub-type of Hollow, Shadows can access and use a Vizard's hollow abilities.
 * Arrancar: Arrancar hosts are possibly the most dangerous, as Shadows can access not only their normal hollow abilities, but their Resurrección  as well, due to it being a natural ability for Arrancar, unlike Shinigami who possess a separate, sentient spirit for their Zanpakuto.
 * Quincy: There have been no known Quincy hosts, so whether or not they retain their abilities is unknown.

Destruction
A shadow can be killed by first snapping the membrane in their hollow hole, then destroying their mask. They can also be incapacitated by severely injuring them, but the first method is the only way to get rid of one. If the membrane is not snapped before destroying its mask, the shadow can simply regenerate. It is rumored that shadows no longer have any discernible facial features besides their mouths and an opening for their nasal cavity under their masks.

Trivia

 * A shadow's soul has been so eroded that there is usually nothing left, preventing reincarnation.
 * Shadows that are strong enough to take on the appearance of souls they have consumed have each soul's memories, but cannot remember their own name.