Innocence

Innocence, also known as Anti-Akuma Weapon when invoked by an Accommodator and as the Crystal of God by those who first used it seven thousand years ago, is the power source that drives the Black Order. Innocence is also the weapon that Exorcists use to defeat and purify Akuma.

Innocence is used by exorcists chosen by the innocence to wield them (they appear to them in a form of a humanoid or animal-like creature). Each piece of innocence is different and is specifically created for their use. Innocence is somewhat sentient and can make up it's own mind who it will use as a host or something else.

One part of the Black Order's agenda is to find all of the Innocence shards as well as their compatible users to defeat the Earl and his followers. The Innocence is the only thing that can destroy Akuma without destroying its soul, and hurt the Earl and members of The Noah Family, the Noah and Earl have the ability to destroy shards of Innocence by crushing them in their hands. At least 12 pieces of Innocence have been destroyed by them so far.

If a piece of innocence has decided that the one using it has sinned or will not recognize the current user anymore as it's master, the exorcist will become a fallen one. This is where the innocence completely takes over an exorcist's body and turns it into a monster, destroying everything surrounding it. There is no current cure for this and eventually the one afflicted will burn out and die in 24 hours. Allen managed to stop Suman, a fallen one, by removing the innocence itself from him but by then Suman's mind was already dead and he had become a comatose, non-responsive person.

History
The Innocence was originally a golden cube, inscribed with what is described by Hevlaska as an ancient prophecy: ''Our descendants, We have battled the darkness, and they are a dying breed. There will be calamity in the future, so we leave behind this message here in order to help you.'' It is revealed that the cube was made by people who had fought the Millennium Earl, and in the process the world was destroyed by a great flood, where only Noah and his family survived. The Innocence was eventually scattered into 109 pieces around the world.

Synchronization Rate
The power of innocence is determined on how much an exorcist is in sync with his weapon. The higher the synchronization rate, the better and more powerful the weapon is. Also, Exorcists who have achieved a certain sync rate with their Innocence can advance it to Level Two if necessary. This can allow them to access more powerful skills that cannot be used at basic invocation. Most exorcists have a synchro rate of about eighty or more. Generals are the only ones that can bring their rates up to one hundred percent and beyond that. Those who can exceed a 100% sync rate will be capable of becoming general. Syncro-ratio that goes above 100% is called the critical point.

If a sync rate falls below ten percent it is too dangerous for user to use the weapon, and when the syncro-ratio reaches 0% the exorcist becomes a Fallen One.

Innocence types
There are three types of innocence forms:

Equipment
The most common of the innocence forms. This is where the innocence is forged into a weapon and is used by the chosen exorcist. Each equipment innocence is forged differently to accommodate each exorcist's unique innocence abilities, such as Kanda's sword or Lenalee's boots. Because the Innocence is not physically in contact with its Equipment-type Accomodator, the Exorcist cannot control the weapon as well as a Parasitic-type can. Additionally, it is revealed in the anime that members of the Noah family can extract the Innocence from equipment-type weapons easily if given the chance.

Parasitic
A rare type of innocence where the innocence is with the person from birth and serves as a weapon. Though the cells that make up this type of innocence are not part of the person, the body still recognizes them as its own. Exorcists with parasite-type innocence have higher sync rates with their innocence. As the Innocence is a part of the Exorcist's body, it can heal the Exorcist if he or she is hit by the Akuma's Blood Bullet, destroying the virus before it spreads. Parasite-type exorcists require high amounts of food and nutrients to sustain themselves, as they are technically eating for two. It has been revealed that Parasite-type exorcists have a shorter lifespan than Equipment-types due to their Innocence taking a much larger toll on their body than an Equipment-type user's Innocence would. The people with the Parasite-type innocence usually have the innocence imbedded in their skin to form their anti-akuma weapons.

Crystal
A new type of innocence where blood is the innocence's medium. The power of this type is incredible as Lenalee used this type to help defeat a level four Akuma. The full power of this type has yet to be seen. There is no telling what this type will do to the person in life. Currently the order is recording all uses of this type and finding out what it can do as well as what would happen to the person using it. Although the Innocence can be controlled through emotions like a parasite-type, no part of the user's body is altered. Instead the Innocence resides in the crystals made from the Exorcists blood forming an object such as a ring, or in Lenalee's case, a pair of bangles around her ankles. When the user activates the innocence, the item transforms into a weapon of sorts, similar to equipment-type, but not actually part of the body like the parasite-type.

Lenalee's innocence is the only crystal type in the series so far.

Apocryphos
An innocence that the Millennium Earl refers to as Apocryphos, and is apparently neither human nor an Accommodator. It is an independent Innocence that only exists to solely protect the Heart. The full extent of it's powers is unknown, but is does seem to have a will of its own and is capable of taking human form. It is also shown to be able to erase the memories of others, though if there will is strong enough they can resist temporarially, in addition to the ability to absorbe others, as it stated its current goal was to absorbe Allen.

Heart of Innocence
The Heart of Innocence is a shard of Innocence that contains the source of power of all Innocence shards. It is unknown what it exactly looks like but it has been speculated that the Heart holds much more power than an ordinary Innocence shard and reacts in even stranger ways than usual. However, should the Heart be destroyed, every other piece of remaining Innocence would shatter along with it. Currently, both the Earl and the Order are trying to find the person who has it and or where it is. The side that finds it first would hold a large advantage over the other, and finding it is one of the key agendas of both sides.

Lenalee Lee was thought to be the wielder of the Heart because of the way it protected her after her first battle with a Level 3 Akuma. However, this was because it was the first case of an Innocence acting sentiently. When Allen Walker's Innocence restored his heart in a similar fashion, it raised doubts to Lenalee's case, though her evolution to Crystal restored hope that the Dark Boots were the Heart.

The Earl has his own thoughts on the matter. He believes that the Heart is sentient and is influencing other Innocences to make a "dummy Heart" in order to mask its true identity.

So far Lenalee and Allen's innocence are the only innocence believed to be the "Heart of Innocence", though Allen's case has come into question given his attack by Apocryphos.