Dark Matter

Dark Matter (暗黒物質 (ダークマター, Dāku Matā)) is the polar opposite of Innocence and serves as the power source for both the Noah Family and its Akuma servants. It was also used by the Black Order to make Third Exorcists.

Overview
Dark Matter is a substance of a malignant nature that damages the living flesh of non-Akuma and non-Noah. It causes the Blood Oil of Akuma to have the "blood virus" effect, which causes all living things, from humans and animals to plants, to break out in typically pentacle-shaped markings before their bodies solidify and they break. It also causes the gasses that rise from the spilled blood of Akuma to be noxious.

As Akuma kill, the Dark Matter within them evolves and strengthens them, causing Akuma that reach Level 2 and onwards to develop specialized abilities. As the Akuma evolves, the Dark Matter also erodes more of the soul trapped within the Akuma, to the point where when they reach Level 4 their souls are so deteriorated Allen Walker cannot bear to look at them.

Akuma
All Akuma are created from a skeleton of Dark Matter, which acts to bind the souls of the recently departed to the skeleton and forces them to obey the Earl and the Noah, even if it visibly against their will. As an Akuma evolves, so does the Dark Matter that comprises it. As the Dark Matter evolves, the soul within the Akuma deteriorates. The later Akuma evolutions are described as having souls in such states that Allen Walker, who has been seeing Akuma-bound souls in varying states of deterioration for years, became physically ill. If an Akuma is killed by anything other than Innocence, then the soul powering the Akuma is consumed by the Dark Matter and lost forever.

Akuma have shown a variety of abilities as they and the Dark Matter comprising them evolves. Level 1s have a common Akuma Blood Bullet ability in which they fire bullets containing a poison which even a small amount rapidly deteriorates and kills the victim. Level 2s have individualized powers, such as elemental control, physical morphing and sound manipulation. Level 3s seem to bring the variety back into a more grouped area of powers, where they use the pure power of Dark Matter in an energy form itself to create unique abilities. Level 4s have shown no real unique abilities amongst individuals as yet but they do have several shared abilities; they can create and fire Akuma Blood Bullets, use an Akuma scream capable of knocking even a General-level Exorcist down to their knees and fire Dark Matter energy bolts.

The Noah Family
The Noah Family use Dark Matter to give them their unique supernatural abilities and all of their powers are based off it. Because of this, they are both vulnerable to Innocence and yet also Innocence is vulnerable to them; the Noah are capable of easily destroying Innocence shards with their bare hands. The separate, unique abilities of the Noah with the Dark Matter are as follows:
 * The Earl of Millennium: The Earl's abilities range from Akuma creation to expansive blasts of Dark Matter energy. His special dark matter ability is that of devouring human souls with appendages from his fingers. The Dark Matter he uses to make akumas is actually pieces of his own soul.
 * Tyki Mikk (Pleasure): Tyki's Dark Matter-granted ability is designated "Choose", which allows him to choose what he does and doesn't want to touch effectively determining what he wishes to affect him; this can range from skin to solid, inanimate objects to even the air. He uses this ability to store his Teez within his body, and he can also "repel" anything in his path, creating powerful explosions using air compression or creating absolute vacuums about his target to suffocate them.
 * Sheril Kamelot (Desires): Sheril's Dark Matter allows him to use invisible "strings" to control the bodies of others, and the pull of these strings is so powerful he can break limbs and, as described by Sheril, "bend [people] into horrible shapes".
 * Wisely (Wisdom): Wisely's Dark Matter powers manifest in the "Demon Eyes" that form from the stigmata on his forehead, with which he can explode/implode the brains of his targets, read the minds of others, and force people to relive memories.
 * Fiidora (Corrosion): Fiidora's Dark Matter manifests in the form of multiple, eyeball-like "parasites" on his tongue, which he can inject into victims that can wreak havoc on their bodies from the inside or can remain benign and be used for surveillance purposes.
 * Skinn Bolic (Wrath): Skinn's Dark Matter ability is called "Wrath of God", which allows him to generate powerful, lightning-based attacks and coat his body in a thick,golden armor-like shell. He can also infuse his powers in others to manifest "chains" that allow him to attack his targets from the inside out.
 * Road Kamelot (Dreams): Road's Dark Matter ability is called "Dreams", and it allows her to separate herself from reality. The Road that is typically seen in the material world is rarely the real Road, and the only way to truly harm her when she is like that is to attack her "true body", which, whatever it happens to be at the time, is often disguised and hidden in her dream world.
 * Jasdevi (Bonds): Jasdevi, who is often split into the bodies of the twins Jasdero and Devit, calls his Dark Matter-driven power "Materialization", which allows the twins, when they are split, to create something by thinking of it silmultaneously, and, when they are joined into Jasdevi, to further condense that same power by focusing it with the one, joined mind. Jasdevi, though, is still bound by certain basic laws; for example, even when imaging himself possessing the "strongest body imaginable", he is still vulnerable to Innocence.
 * Lulu Bell (Lust): Lulu Bell's Dark Matter power is called "Shapeshift", which allows her to change her body into any form she wishes.

Third Exorcists
In order to strengthen their forces, certain powers in Central deemed it necessary for the Black Order to utilize the Dark Matter as a weapon, resulting in the creation of the Third Exorcist Program.

The Third Exorcist Program combines humans with Akuma cells, genetically altering them to use Akuma abilities based on the Dark Matter. They are able to transform their left arms into Akuma-like appendages, which increase their physical strength and allow them to cannibalize Akuma, which destroys the soul of the Akuma.

Trivia

 * In physics, Dark matter is an unidentified type of matter whose existence would explain a good part of physics interactions.