Fallen One

Fallen Ones (咎落ち, Togaochi) are people whose synchronization rate with Innocence falls bellow 0%. This can happen for a number of reasons, such as a non-host person attempting to force a connection with Innocence (which is a forbidden experiment now), or an Exorcist who betrays the Innocence (essentially one who betrays the Innocence/God and the Black Order).

Once somebody becomes a Fallen One, they are effectively dead as no one has ever successfully revived a fallen. Allen Walker was able to save Suman Dark by removing his body from the Fallen One, but Suman's mind has already died. It is not known if that is an inevitable conclusion or if it is just because he was too late in in rescuing Suman.

Personalities
Fallen Ones are basically mindless killing machines who wish to destroy everything with out discrimination. Despite this the hosts personality can reawaken, as shown by Suman Dark, but even if it does, the host has no control over the actions of the Fallen One, and can only watch helplessly in pain as it destroy everything in sight. This ironically is very similar to the behavior of akuma.

Appearance
So far, Suman Dark is the only exorcist known as Fallen One. He takes the form of a massive white floating torso with huge holes at both shoulders as well as at the top of the neck and a single hole below the waist. Floating above the neck hole is a large halo. At the location of the heart there is a porous material is a twisted and tormented version of the host. Where the waist should be there is a large number of pipe-like protrusions forming a large flat area at the base of the torso. The porous material can be penetrated by an external person, to which they can go inside the Fallen One where they will be barraged by the memories and thoughts of the host. Inside is a large open space which appears to be filled with some sort of liquid and the Innocence that controls the host can be seen.

Powers
Fallen Ones are some of the most powerful entities to be seen in the series so far. They are created by the Innocence going berserk in their bodies, and thus are fueled not only by the Innocence itself, but also by their own life energy. The side effects of this are that the host is in considerable pain and will burn out and die in about 24 hours. Their minds also die out even if their bodies are removed before death.

Fallen Ones attack by launching massive energy beams out of the arms, head, and legs holes which destroy anything they touch. The Fallen One form of Suman Dark is shown destroying hundreds of Level 2 Akuma in a single attack as well as a couple of mountains. On top of their massive attacks, Fallen Ones also boast powerful defenses. They are able to withstand massive quantities of fire power almost without injury.