Reiatsu

Reiatsu is the physical pressure that a spiritual being's Reiryoku emits when released. This release can often be manipulated by Shinigami, Arrancar, Quincy, Fullbringers and Bounts.
While Reiryoku and Reiatsu are often spoken about together, the two are very different. Reiryoku is the amount of spiritual energy that a being has stored within their body or soul, while Reiatsu is the pressure that a being's spiritual power exerts. This means that Reiryoku is potential while Reiatsu is energy that is in use and can be sensed by other beings that are spiritually aware.
Those with a high level of Reiryoku often have the highest levels of Reiatsu. A skilled warrior can overcome a person with greater Reiryoku by having greater Reiatsu. This is achieved by having greater control over one's spiritual energy.

Reiatsu Vents

All Shinigami have places on their wrists that serve as vents for their Reiatsu. If these places are blocked, the Shinigami in question can be incinerated by their Reiatsu from within.

Reiatsu Release

The Reiatsu released by individuals eventually returns to them, but Reiatsu released in explosive bursts will engulf energy in its surroundings in the process.

Spirit Class

The density of Reiatsu within the Reishi of a given Soul determines their Spirit Class, a number ranging from 1 to 20 with the densest Reishi and most powerful individuals having a lower number. Lieutenants of the Gotei 13 are often of rank 4 or 5 while captains are at ranks 1, 2, and 3. Those with a Spirit Class of 3 or higher have extremely dense Reishi that cannot be broken down and returned to the soil of the Soul Society after death like other Souls normally do. As it is a large risk to leave such Reishi in the Soul Society, a special form of Konsō is performed to send those of such high Spirit Class at the time of their deaths into Hell.

Uses

Reiatsu and its power can be used in a variety of ways. While offensive and defensive uses are more common, it is possible to use one's Reiatsu to create psychological effects such as paralysis.

Defensive Use

During combat between two spiritual beings, the one with the weaker spiritual pressure will be injured. Because of this, a Shinigami with a greater amount of Reiatsu can use their own spiritual pressure to harden their skin and create armor to protect themselves. Battles between Shinigami are battles of spiritual pressure. If one possesses a greater level of Reiatsu, then one can overcome the other completely. It is also possible to concentrate one's Reiatsu to repel attacks.

Psychological Use

Fear
Reiatsu, at its most basic level, has the ability to instill fear in others when the Reiatsu being emitted is higher than the one feeling it. The best way to fight this effect is willpower
Stun
High levels of Reiatsu can cause those with lower levels of spiritual pressure to be stunned by being in the presence of a high-level spiritual being.
Paralysis
If a high-level spiritual being chooses, they have the ability to paralyze an opponent by focusing Reiatsu through their stare or presence.
Phantom Pain
A spiritual being emitting high levels of spiritual pressure can make their opponent feel phantom attacks, even if they are not being attacked physically.

Offensive Use

Physical Damage
Reiatsu can be transferred through weapons and other methods to cause physical damage to opponents.
Lethal Damage
In enormous quantities, Reiatsu has the potential to be lethal to others.

Kanji

霊圧

English

Spiritual Pressure

Type

Metaphysical, Arcane

Reiatsu Sensing

The senses that a spiritual being uses to feel and pick up on Reiatsu are known as Reikaku or Reiatsu Chikaku. Those who have Reiatsu subconsciously use their vision and their Reikaku at the same time in order to see. When concentrating during battle, Reikaku takes over a spiritual being's perception, essentially allowing the being to subconsciously see without their eyes.

Appearance

Reiatsu Colors

Different spiritual beings have varying colors of Reiatsu. This property of the Reiatsu is not dictated by an individual's race or power. Over time, the color of one's Reiatsu might change, or the Reiatsu might change colors while using certain abilities.

Shape

Reiastu, when released, can be seen in a shape or manifestation if enough energy is released from an individual. These manifestations are often ones of the inner strength of a spiritual being.

Types of Reiatsu

Standard Type

The most common form of Reiatsu. It has no special abilities beyond what all Reiatsu can do and its color and feeling are still unique to its user. Quincy and Humans always have this type of Reiatsu, while most Hollows and Shinigami also have this type. Other races, such as Fullbringers, are Humans that have Hollow-like powers, but they still have standard Reiatsu.

Dual Type

Certain races, such as Arrancar, have special Reiatsu known as dual type. This is because certain abilities of these races take on the feel of other races, such as Shinigami.

Elemental Type

This is a rare type of Reiatsu and has been known to have been used by a small few. This type of Reiatsu is these people's natural power and manifests in some elemental way.