Voids are spirits that have undergone a process known as "the Total Collapse" and have literally lost their existence. Normally, when a Plus turns into a Hollow, it develops emptiness inside itself (this emptiness is signified by the Hollow's hole). In normal cases, this emptiness reaches balance within the spirit. But, in some cases, the emptiness fails to reach the balance, and continues to consume the spirit until nothing is left of it except the emptiness: A Void has been created. Voids are normally very rare occurrances.
It should be noted that the very existence of Voids endangers the balance and therefore existence of the entire world. This is because Voids absorb reiryoku all the times. The reiryoku absorbed by Voids is permanently lost and is removed from the world's spiritual circulation for good. The longer Voids exist, the more they absorb and the more the balance is disturbed, eventually leading to the world's destruction, if the Voids are left to exist. Thus, all Voids are deemed to be exterminated on sight.
However, destroying Voids is harder than dealing with Hollows or Pluses. They are not harmed by regular cutting attacks from Shinigami Zanpakuto, and with their reiryoku absorption they are mostly immune to all Kido and Zanpakuto techniques. However, there is a way to destroy a Void: To "overload" it with reiryoku. If the Void is fed more reiryoku than it can absorb, its emptiness is partially or completely filled, thus damaging or destroying the Void.
Reiryoku Absorption: As stated above, Voids constantly absorb reiryoku from their surroundings. Because Voids are made of emptiness, they don't have their own reiryoku and can be sensed by spiritual creatures from their constant "suck" of reiryoku.
Emptiness Consumption: In addition to absorbing reiryoku, Voids can also absorb other Voids to make their own emptiness greater, thus increasing their power and ability, much like Hollows do.
Intangibility/Extreme Regeneration: Formless Voids are intangible and thus immune to physical damage. To replace their loss of intangibility, formed Voids have extreme regenerative capabilities, even being able to grow back together when blown to pieces or regenerate from a single surviving limb.
Void Energy Manipulation: All Voids have certain abilities at mastering the very emptiness that they are made of and using it as a means of attack or defense. With stronger Voids, their abilities to use their Void energy are usually those of higher grade.
- Void Blast: General attack with Void energy, comparable to Cero. This attack will incinerate any spiritual matter not resistant enough on its path. It is possible to resist Void Blast with enough spiritual power.
Voids can be classified into several categories. These two form the main classes of Voids:
- Formless Void: Formless Voids are Voids that are so weak they fail to reach a tangible form, and thus stay in forms that are like black clouds trying to reach a form. Most weak Hollows or other spirits transform into Formless Voids if the undergo the Total Collapse. Also, if the spirit undergoing the Total Collapse lacks consciousness, it will turn into a formless Void.
- Formed Void: Formed Voids are Voids that are strong enough to reach a tangible form. They have more power than formless Voids and also have consciousness, and are thus considered much more dangerous than Formless Voids.
There are further categorizations for Voids. Voids of these categories can be both Formless or Formed:
- Hollowborn Void: The name for a Void born from the Total Collapse of a Hollow, resulting from the inner emptiness of the Hollow overcoming and consuming it. Hollowborn Voids can be further categorized in categories corresponding to those of Hollows (ie. "Menos born Void" etc.). Hollowborn Voids are the most common type of Voids.
- Inner Void: Inner Voids are much rarer and usually also stronger than Hollowborn Voids. This is because inner Voids are a type of Voids to be carried inside a soul, creating a huge burden to the soul forced to bear the inner Void. Inner Voids can give their bearer Hollow-like power because they work like the inner emptiness of a Hollow inside their host, with the exception that inner Voids have taken a form and are conscious. Inner Voids usually mirror the powers and abilities of their hosts. Inner Voids constantly try to consume the soul they are in, and in most cases only succeed partially, making the soul that bears them a Hollow by merging their emptiness with their host's soul. However, in some rare cases the inner Void manages to completely consume their host, creating the rarest and most powerful of all Void classes, the Reject.
- Reject: As described above, the Rejects are the rarest and the most powerful type of Voids, born when an inner Void manages to completely consume its host. Not much is known about Rejects due to their rareness, but it is known they possess both the powers of the former host-soul and the inner Void, essentially making them at least twice as strong as their former hosts.