The Fallen

The Fallen are human souls that have been possessed and claimed by the Darkness that covers Kaldor. Different humans experience this transformation in a number of ways.

Descended
When a Reaper's soul has become fully immersed in the darkness, their physical body falls apart and their mind collapses, leaving behind a massive, extremely powerful unseen beast known as a Descended. The Descended are characterized by their Reaper blade, which is fused with their bodies. It is unclear if whether or not slaying a Descended frees the Reaper from the Nightmare.

Twisted
The Twisted are ordinary people who were claimed by the Darkness. It is unclear what causes some humans to become Twisted upon death. Unlike the Descended, the Twisted retain some semblance of intelligence - they are capable of speech, though they lack humanity. They, like the Descended, appear to have only one interest - feeding off of the souls of living people.