Zanpakutō

A zanpakutō (斬魄刀, Soul-cutter sword) is the primary tool and weapon of the Shinigami and the Arrancar, though their function in each group differs. The art of using the zanpakutō in it's regular sword state is called zanjutsu (斬術, swordsmanship).

Overview
The zanpakuto is the primary weapon of the Shinigami and the Arrancar. In thier base state they have the ability to cut any type of spirit body. Shinigami primarily use thier zanpakutō to fight their mortal enemies, Hollows. Zanpakutō are one hundred percent unique in both Shinigami and Arrancar. In Shinigami, the zanpakutō is a manifestation of their soul and inner power. For this reason, zanpakutō tend to vary in appearance so as to reflect the personality of their Shinigami. Another interesting feature of Shinigami zanpakutō is that they are sentient beings. A being called a Zanpakutō spirit inhabits the Shinigami's "Inner World" and empowers the sword, thus lending it's Shinigami it's power. A zanpakutō also has it's own name. When a shinigami learns his or her's zanpakutō's name, they can achieve new heights of power. Zanpakutō cannot be replaced, however, they can regenerate if damaged and given enough time. Lastly, a Shinigami's zanpakutō has it's own, separate, reiatsu that feels almost identical to it's wielder's with subtle differences.

Asauchi (浅打ち, shallow hit): The class of nameless Zanpakutō that all low-class Shinigami wield. Shinigami who are still in training - those who do not yet belong to any of the Gotei 13 - all wield generic Zanpakutō. Shinigami who are unable to communicate with their Zanpakutō, the "shallow hit", which refers to the grossly-reduced power of a Zanpakutō whose wielder cannot connect with it properly.

In Arrancar, the zanpakutō is not a manifestation of the user's soul, but instead is an Arrancar's Hollow powers sealed into sword form. Just like in Shinigami, Arrancar zanpakutō take a wide range of shapes and sizes.

Obtaining a Zanpakutō
In Shinigami, a zanpakutō is generated when the reiryoku of it's Shinigami is solidified into sword form. After the Shinigami graduates from the Shinō Academy is usually when they have enough control to preform such a feat. Soon after gaining their zanpakutō in it's asauchi stage, the Shinigami will learn it's name and become able to activate it into a stage called "Shikai".

In Arrancar, soon after they are created from Hollows, they are able to seal their Hollow form and it's powers into the form of a sword. It is unknown exactly how an Arrancar's zanpakutō is named, but it is known that they do not have inner spirits. Immediately after the zanpakutō is created and Arrancar is able to use their own type of release; called the "Resurrección". It restores and Arrancar's hollow form as well as gives them great amounts of power.

Forms
A zanpakutō can manifest it's power in a total of two forms for both Arrancar and Shinigami. In Shinigami, these forms are called Shikai and Bankai. In Arrancar, it manifests in the forms of Resurrección and Resurrección: Segunda Etapa, though in the case of the latter it has only been seen once. In Shinigami, the ability to release thier swords depend on their skill level. Shikai is gained generally at a pretty early stage. Bankai, however, takes tremendous skill to master.

In Arrancar, the Resurrección form is inherent. It is already known from the moment an Arrancar can form it's zanpakutō. Resurrección: Segunda Etapa, however, has only been displayed in Ulquiorra Cifer. According to Ulquiorra, he developed a "second sword release" himself. This implies that Resurrección: Segunda Etapa must be individually created by the Arrancar, but requires tremendous skill and control.

Sealed Form
All zanpakutō begin in a "sealed state", which most commonly take the form of a katana, though other types have been seen such as;
 * Katana: The term katana may be applied to the standard-size, moderately-curved, Japanese sword with a blade length of greater than 60 cm (23.6 inches). The katana is characterized by its distinctive appearance: a curved, slender, single-edged blade, a circular or squared guard, and a hilt long enough to accommodate two hands.
 * Wakizashi (脇差 (わきざし), side insertion): A short blade between 30 and 60 cm (12 and 24 inches), with an average of 50 cm (20 inches). It is similar to, but shorter than, a katana, and usually shorter than the kodachi (小太刀 (こだち); meaning "small sword"). The wakizashi was usually worn together with the katana. When worn together the pair of swords were called daishō, which translates literally as "large and small". The katana was often called the long sword and the wakizashi the companion sword.
 * Nodachi (野太刀 (のだち), field sword): The nodachi was more difficult to wield due to its size and weight. The length of the nodachi's hilt varied between twelve to thirteen inches (30 to 33 centimeters). Its cutting capability and range exceeds that of a katana, due to its weight and size.

In addition to their base form, the zanpakutō can be disguised as other objects such as canes and staffs. They are usually carried in a sheathe which is kept on the Shinigami or Arrancar's person, but occasionally certain individuals will carry them in different ways; such as by Kidō, in the case of some Shinigami, or just simply carrying it around, like some Arrancar. If a Shinigami is knocked out, their zanpakutō reverts back to it's sealed state. In the case of Arrancar, the zanpakutō will only revert to sword form if the Arrancar reseals it's hollow powers again.

Shikai
Shikai (始解, Initial Release) is the first transformation of a Shinigami's zanpakutō. In order to utilize it, a Shinigami must know the name of his or her's zanpakutō. This is no simple feat, as the shinigami cannot just pick out any name they want; their Zanpakutō already has a name. To learn it, the shinigami must be able to communicate well with his or her's Zanpakutō spirit.

To activate the shikai afterwards, the Shinigami will recite a command or command phrase which is usually followed by the sword changing shape and it's Shinigami's spiritual power rising. This step can be bypassed if a Shinigami knows Bankai. Most zanpakutō remain in the form of a sword in shikai, however, it has been documented that some zanpakutō change form into completely different weapons such as flails, stingers, naginata, and scythes. In rare cases, some zanpakutō remain in their shikai state permanently. This is present only in Shinigami who have vastly uncontrollable reiatsu upon the initial generation of their zanpakutō. In Shikai, a zanpakutō gains unique abilities which a Shinigami can utilize in combat. Like the zanpakutō, these abilities have names that must be learned in order to grant them more power.

Bankai
Bankai (卍解, Final Release) is the final form of a Shinigami's zanpakutō. To use a Bankai, one must be able to materialize their Zanpakutō spirit in the real world. This process usually takes about ten years to master, though this does not take into account the power needed to master it. Though the power and abilities of a Bankai depend on the user's experience and control, it generally increases it's master's power by five to ten times.

Only Ichigo Kurosaki and Kisuke Urahara have mastered it in a shorter time. They both mastered their Bankai in three days due to a technique Urahara invented. Unlike in shikai, Bankai does not require a release phrase in order to activate it, though the shinigami will usually say "Bankai" before activating it. Like with shikai, the forms a Bankai can take is completely unique to it's user. It is usually a manifestation of the zanpakutō's spirit, such as a creature or a massive effect that assists the user in combat. Ichigo's Bankai is an exception to this, as it shrinks down and compresses. A Bankai will also receive a different name in addition to it's original name.

The abilities of the bankai generally stick with the theme of the shikai's abilities, but greatly increases it's power level.

Resurrección
Resurrección (帰刃 (レスレクシオン), resurekushion; Spanish for "Resurrection", Japanese for "Returning Blade") is the zanpakutō release technique of the Arrancar. By saying the release phrase of their zanpakutō, an Arrancar can regain thier true form as well as their Hollow powers. Most Resurreccións give Arrancar animal-like features. While most sealed zanpakutō still take the form of katana, the sealed forms of Arrancar zanpakutō seem to have a much wider range of appearances, such as axes, a sai, and some more unique weapons. Most arrancar loose their weapons upon the release, but a few get upgraded versions of their previous weapon. They also gain new abilities, as well as upgrades of their Hollow abilities, such as Cero and Bala. The power level of a Resurrección is comparable to the Bankai level of a Shinigami.

An Arrancar can only return to their Human form once they reseal thier Hollow powers. Doing so without resealing is permanent and is akin to loosing one's limbs.

Resurrección: Segunda Etapa
Resurrección: Segunda Etapa (刀剣解放第二階層 (レスレクシオン・セグンダ・エターパ), resurekushion segunda etāpa; Spanish for "Resurrection Second Stage", Japanese for "Sword's Release: Second Level") is a more enhanced form of Resurrección. So far, it has only appeared in Ulquiorra Cifer though it may be entirely possible for other Arrancar to achieve this stage as well. Spiritual power in the stage is said to be overwhelming. Speed, strength, and stamina are also improved immensely, and the form of the Arrancar becomes closer to that of a Vasto Lorde-class Hollow.