Black Box

The Black Box (ブラックボックス, Burakkubokkusu), also known as The Devil's Heart (悪魔の心臓, Akuma no Shinzō lit. Heart of the Devil), is a sealed dark colored cube and the only one in existence. It is currently in the possession of Oz.

Overview
The Black Box is said to origin for longer than thousands of years ago, how it was created or who created it is unknown, though it has been mentioned that it was made from several "things". It is smaller than a human fist that it can be easily hid behind one's hand.

Activation
In order to activate the Black Box's powers, one must make the Black Box replace his/her own heart, and so that the Black Box can feed off the user's spiritual energy and life force to allow him/her to use the powers. Two general ways of doing so are known, the basic and more traditional way has been known to be performed with the help of a partner, who would push the Black Box through someone's chest until it entered the body then leave the Black Box and pull out the heart, surviving this process grants the user the powers of the Black Box.

The second, and less risky way of activating the Black Box's powers, which can be done alone, is to swallow the Black Box whole and hope it reaches the center of the chest to take the heart's place, though the heart remains in place only dead with the Black Box operating in a same manner as the heart.

Humans and Quincies are noted to have the lowest chances of surviving either one of these implantation process, because they would die from having their hearts pulled out immediately by the first process, and can choke in the second process.

Powers
Once the implantation is done, the user gains several abilities, though the limit of abilities is unknown, though it has been stated that the Black Box's full power can destroy even the strongest of the Espada's body into mere dust and that only 5% of the Black Box's powers can be used without harm done to the user. The powers are as followed:
 * Second Skin Layers: The user gains a second layer of skin under their original skin, which is dark colored and highly durable, needing great force to shatter. However that doesn't keep the user's own skin safe as it is still normal skin which means the user feels the pain of having his/her skin piercing or cut.
 * Reishi  Crystallization : A unique ability gained from the Black Box, the ability to crystalize reishi into a dark crystal-like form, however it is only limited to the user's left arm because that is the direction the heart is located at, unless on rare circumstances the heart is in the right. The user also cannot manipulate the crystalized reishi. It is also possible for one to crystalized spritiual beings that their bodies are composed off reishi and are much weaker than the user.
 * Power Augmentation: Using the Black Box also enhances the power of one's power, for example, a Shinigami's Zanpakutōbecomes more powerful and also gains a change in appearance, which is by having black crystals growing from some parts of the Zanpakutō, the same goes for an Arrancar's Resurrección and a Quincy'sSpirit Weapon.
 * Regeneration: The ability of regeneration that takes only a few seconds to heal any one of the user's wounds but does not remove the feeling of pain, the user is also still killable if hit by a lethal wound.
 * Hollow Purification: The black crystals can seemingly purify Hollows, just like how Shinigami's do with the use of Konsō.

Side Effects & Weaknessess
The Black Box has several known side effects and weaknessess from using its powers, first of all, because of the ability to crystalize reishi, attacks such as Cero, Kidō spells, and Gintō would still be accessible but would crystalize after being used which would make them useless, though it doesn't appear to affect other reishi related abilities.

As mentioned before, using the Black Box's powers is only accessible if the user can use either his spiritual energy and/or life force as the catalyst, which means that over using the Black Box's powers can shorten the user's life and spiritual energy, though the Black Box primarily begins using the spiritual energy as the catalyst and uses the life force after the spiritual energy is all drained out.

Effects by Races
The Black Box has a different effect on each race, since each race does have its own unique attributes and powers, the Black Box can affect them as well.
 * Arrancar: When used by Arrancars, the Black Box enhances all of their powers, including Resurreción. It doesn't cause much changes in appearance, but is very noticeable when it comes to their Resurreción having some crystals on them and their cero becoming pitch black in color.
 * Shinigami: A Shinigami doesn't gain much difference in appearance, only their Zanpakutō, being dyed in black or having some crystallizations on them.
 * Human: Humans are the only race that cannot survive the implantation of the Black Box, the two main reaons being that Humans cannot sruvive long when their hearts are pulled out and the other reason being they cannot handle the power of the Black Box, which destroys their body and soul into nothing, similar to when a Quincy kills a Hollow.
 * Quincy: Out of all the other races, Quincies most likely have the most advantage in using the Black Box, the reason being they can absorb and manipulate reishi, and since the black crystals are technically crystallized reishi, Quincies are the only ones whom are capable of freely manipulating them. Their spirit weapons, and other abilities, are all enhanced. Also, it grants the Quincies the ability to emit spiritual energy, which comes from the Black Box itself, so it isn't technically the Quincy's spiritual energy is simply given by the Black Box. It should be noted that since Quincies aren't ordinary Humans, they can survive the implantation proccess.

Trivia

 * The Black Box, along with most of its abilities, came to me in a dream.
 * The image of the Black Box was to me by User:SecretGeneration, all credit goes to him for his awesome job.