Kidō

In the manga and anime series Bleach, kidō (鬼道) are a form of magic used by Soul Reapers.

Overview
Kidō spells are used by Soul Reapers in the fictional world of Bleach for various purposes. Spells exist for attacking, binding, and healing. Like conventional magic, most of these spells require an incantation of some sort to activate their effect. They are performed through channeling spirit energy, which the incantation then focuses into a specific effect. As stated by Ganju Shiba, the principle behind kidō and channeling spirit energy in general is a mental image of throwing oneself within a darkly-colored circle.

Most kidō spells are sorted into two categories: binding spells (縛道) and destructive spells (破道). The former category is somewhat more generalized, referring to basically any technique designed to deter a target, including tracking and communication spells. Some binding spells, however, can be quite harmful to their targets, if not deadly. Destructive spells, on the other hand, are always intended to harm, usually consisting of some sort of directed energy blast.

With the exception of healing, which requires no incantation or even a name to perform, kidō spells consist of four distinct steps: reciting the incantation of the spell (which is usually long-winded), its category (binding or destructive), its number, and finally its name. The number of a spell determines the difficultly of casting it correctly and effectively (#1 is simple to cast, #99 is incredibly difficult). With sufficient training, the first step can be bypassed, allowing spells to be used in combat quickly. Doing so, however, lessens the spell's effect, the degree of which is dependent upon the skill of the caster. Bypassing the incantation is also more difficult for higher-numbered spells, as casting them is already fairly difficult even with the full verbal component. The power of kidō spells varies on the skill of the user; even a low-level kidō spell can be utterly devastating when utilized by a sufficiently powerful user.

Complementing kidō may be combined for a single ability, something that Isane Kotetsu demonstrated when she used binding spell #58 to locate Sōsuke Aizen and Gin Ichimaru within Soul Society, and then #77 to convey the information to every captain and lieutenant (as well as Ichigo Kurosaki and his friends). Rukia Kuchiki has also demonstrated the ability to use two kidō spells simultaneously by alternating between the lines of each incantation.

Kidō can also be combined with other forms of Soul Reaper combat to form unique abilities, such as Yoruichi Shihouin's flash cry (瞬閧) technique, which combines kidō energy and hand-to-hand combat (白打) to concentrate spiritual power at the back and shoulders for quicker movement and increased attack power.

Binding spells

 * 1. Restrain (塞) — Locks a target's arms in place behind their back.
 * 4. Crawling Rope (這縄) — An energy rope entangles a target's arms.
 * 9. Strike (撃) — Engulfs a target in red light, completely paralyzing them.
 * 58. Summoning of the Tracking Sparrows (摑趾追雀) — Tracks and locates any spiritual force the user focuses on. To activate it, the user must draw a circle on the ground, cut into four parts with a specific character in each. The incantation animates the circle, causing various numbers to appear within until the specific set is found. The number set seems to be a variation on longitude and latitude.
 * 61. Six Rods Prison of Light (六杖光牢) — Summons six thin, but wide, beams of light that slam into a target's midsection, holding them in place. Referred to as "Six Rod Light Restraint" in the English manga and "Six Bars of Light" in some of the games.
 * 63. Chainlike Desert (Sajo Sabaku )— The target is wrapped from the neck down in a thick chain.
 * 75. Quintet of 1 kan Iron Pillars (五柱鉄貫) — Summons five incredibly tall and thick pillars to pin a target to the ground.
 * 77. Heavenly Rickshaws in Silken Air (天挺空羅) — Transmits messages to anyone within a specific area. In addition to reciting the spell, the user must draw specific markings on their arms, which are animated by the spell to convey the messages.
 * 81. Splitting Void (斷空) — Creates an energy barrier in the form of a rectangular wall. According to Byakuya, it is capable of stopping destructive spells up to #89.
 * 99, Part 1. Seal (禁) — Binds the arms of a target with spiritual fabric and iron shafts.
 * 99, Part 2. Great seal (卍禁) — This spell covers a target from head to toe with spiritual fabric [first song: halting fabric (初曲・止繃)], stabs them with numerous metal blades [second song: hundred linked bolts (弐曲・百連閂)], and then smashes them with an immense metal cube [final song: great seal of 10,000 forbiddings (終曲・卍禁太封)].

Destructive spells

 * 1. Thrust (衝) — Pushes the target away from the caster.
 * 4. White Lightning (白雷) — Fires a concentrated bolt of lightning from the caster's forefinger.
 * 31. Shot of Red Fire (赤火砲) — Fires a ball of red energy at a target.
 * The English dub uses the phrase "Red Flame Cannon" in conjunction with the Japanese name. It also incorrectly identifies this spell as bakudō 33 in certain scenes, though correctly identifies it in the scene in which it is revealed.
 * 33. Blue Fire, Crash Down (蒼火墜) — Fires a burst of blue spiritual energy at a target in a similar manner to 31, but over a wider area and with more power.
 * 54. Abolishing Flames (廃炎) — Fires a blast of purple spiritual energy that will incinerate a target completely when it makes contact.
 * 63. Thunder Roar Cannon (雷吼炮) — Fires a massive wave of yellow energy at a target.
 * 63. Twin Lotus Blue Fire, Crash Down (双蓮蒼火墜) — Essentially a doubled version of #33, this spell fires two shots of blue fire with greater potency than the single-shot variety. In the anime, Rukia labels this spell as #73.
 * 90. Black Coffin (黒棺) — Forms a box of black energy around a target, which is then pierced by dozens of energy "spears", lacerating the one inside from head to toe. Aizen notes that the spell only reached a third of its destructive potential the one time he uses it, indicating that the spell would be far more damaging at full power. Its appearance and function is reminiscent of a common magician's trick, as well as certain torture devices used during the Spanish Inquisition.

Other
These spells are not explicitly stated to be in one category or the other.
 * White Crawl (白伏) — Momo Hinamori uses this spell while imprisoned to knock out a guard and destroy everything within a certain radius of herself. The anime suggests that it is a binding spell, but doesn't number it.
 * Mirror Door (鏡門) — Tōshirō Hitsugaya used this to seal Momo Hinamori's hospital room. It creates a glass-like barrier which is difficult to break from the outside, but quite simple to break from the inside.
 * Reverse Demon (反鬼) — This technique nullifies an opponent's kidō by hitting them with a perfectly opposite surge of energy. Yoruichi uses this against Soifon's shunkō.
 * Kidō Cannon (鬼道砲) — As the name suggests, the Kidō Cannon is basically a high-intensity energy weapon powered by kidō in Bleach: Memories of Nobody. It consists of a crystalline focus point attached to the top of a massive pole, with several smaller crystal structures circling up towards the main one. It is powered by hundreds of Soul Reapers working in concert, creating an energy blast capable of obliterating a small dimension. The blast forms into several animal shapes which roar just before contact. The power of the blast is such that, in addition to destroying its target, it also causes a small amount of damage to both the human world and Soul Society. Despite its power, it is not a reusable weapon, as it burns into a pile of scrap after being fired.