Kidō (鬼道, "demon way" or "spirit way") is a form of Shinigami combat based on advanced spells. These spells are produced with strong Reiryoku and fall into two categories: Hadō for direct attacks, and Bakudō for battle support. Kidō is one of the techniques in the Zankensoki, the group of Shinigami primary combat skills. Kidō spells are triggered by an incantation. Experienced users can trigger them without an incantation, though the effectiveness of the spell will be diminished.
The Kidō Corps is a branch of Soul Society's military which excels in the mastery of Kidō.
Most spells are graded on a scale from 1 to 99, spells of the latter being the most powerful and the most difficult to perform. To use Kidō, a Shinigami must recite the specific incantation for the spell, which is often long and requires a few seconds to speak.
The power of a spell relies on the power of the user, as even a low-level spell can be utterly devastating when utilized by a high-class Shinigami.
Kidō can be used for practical purposes as well. Renji Abarai has demonstrated that a Kidō spell can be used to light a dark hallway if the spell is tweaked in the right way, albeit with less power.
There are three main types of Kidō: binding spells, destruction spells, and healing spells.
- Bakudō (縛道, Way of Binding): Supplementary spells which can immobilize an enemy or have an effect besides a direct strike. They may seem subtle, but these spells can give their users a tactical advantage when used properly. These are a broad category of defensive spells which block/repel attacks or freezes enemies in place. This class of spells include Kidō Barriers & Seals.
- Barriers (結界, Kekkai): Focused spiritual energy formed into a solid form of energy. This energy can take on many shapes or colors as determined by the user. Barriers are protective in nature, and can be as simple as a barrier only protecting one direction or encompassing all sides of an area. Barriers can be used for containment, and some barriers can be used offensively. Barriers can mask spiritual pressure and can make one spiritually and physically invisible. The strength of a barrier is dependent upon the power of the user. Weak barriers are easily breakable, while strong ones can last for centuries. Barriers created by noble blood are said to be unbreakable by those of lesser status. Certain barriers can be placed beforehand and activated later, while others require certain artifacts and time to activate.
- Seals (封, Fū): Somewhat similar to barriers, but far more powerful and require far more preparation to create. Seals can only be used by those of sufficient spiritual power being who are meant to hold the most powerful and/or dangerous artifacts or beings. Seals are usually hard to break.
- Hadō (破道, Way of Destruction): Offensive spells which inflict direct damage to the enemy. Their effectiveness differs depending on the user. It is said the effectiveness of the higher-ranked spells are beyond imagination.
- Gisei Hadō (犠牲破道, Sacrificial Way of Destruction): A particular offensive spell that requires the user to sacrifice a certain portion of themselves as the cost of using it. Ittō Kasō is one of them.
- Kaidō (回道, Turn Way): Also known as Healing Kidō (治療用鬼道, chiryōyō kidō). These spells do not have known names, numbers, or incantations to cast, and simply heal the target. As the user holds his/her hands above the patient's wounds, his/her palms glow with green spiritual energy to facilitate healing. When one heals with regular healing kidō, they perform Reiatsu restoration first. By doing so, one can attempt to recover the physical body using the patient's restored reiatsu and the healer's external reiatsu. Therefore, restoring the reiatsu when the physical body is in a fully healed state is no trouble at all.
A form of classification for Kidō spells which are considered illegal by Soul Society. The use of such spells will commonly result in some form of lengthy imprisonment or worse. The Kidō spells which fall under this class are those which involve the manipulation of space and time and Kidō which sacrifices the self.
- Eishōhaki (詠唱破棄, Incantation Abandonment): A class of Kidō Incantation where the Kidō practitioner forgoes using a spoken incantation at all. While it decreases the time needed to release the Kidō, it drastically weakens the spell. While anyone well versed in Kidō can use this technique, it is most effective when done by a skilled practitioner, otherwise the spell could utterly fail (e.g. explode in the user's face). The most skilled experts are capable of using this technique to amazing effect.
- Nijū Eishō (二重詠唱, Twofold Incantation): a class of Kidō Incantation where the Kidō practitioner mixes the incantations of two entirely separate Kidō spells together to save time and confuse their opponent at the same time.
- Kōjutsu Eishō (後述詠唱, Spoken-After Incantation): A class of Kidō Incantation where the incantation is recited after initiating the spell in order to power it up.
Kidō is commonly used in instances of surprise attacks, rather than all-out assaults, being most effective when one's opponent does not see it coming. Kidō is usable with just the spell name and no incantation or spell number.