Dark Matter

Dark Matter is the polar opposite of Innocence in the D. Gray Man anime and manga and serves as the power source for both the Noah family and it's Akuma servants, and now also the Third Exorcists of the Black Order. A dark and terrible force, it appears as a black haze that invokes fear and dread in those that see it.

All Akuma are created from a skeleton of Dark Matter, which seems to serve to bind the souls as well as giving them a form. After an level 0 Akuma, a new born one which is just the revived soul in the Dark Matter skeleton, kills its first victim, the person who called them back, the skeleton forces itself into its victim's skin and takes their form. 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 it makes onlooker physically revolted and sick to look at them. 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.

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.

Recently, it was revealed that the Black Order too has the means to use the Dark Matter as a weapon; the Third Exorcist Programs combines humans with Akuma cells, genetically altering them to use Akuma abilities based on the Dark Matter. They are able to use these powers to devour Akuma, the only other real way to destroy them besides Innocence. What happens to the souls of those Akuma destroyed in this way is yet to be known. It is also yet to be shown if the Third Exorcists are able to use the Dark Matter in more exotic and individual power and abilities like the Noah and the more evolved Akuma can.