Poltergeists

Poltergeists are incorporeal entities that manifest as an unseen presence, often confined to a certain area and capable of manipulating solid objects. Their behavior varies on a case-by-case basis, but most of them actively seek recognition and attention for some reason, and will do anything to receive it. According to The Archive, in 92% of the recorded cases of Poltergeists coming into contact with a Fear, they became docile for the duration of the Fear's presence. In the remaining 7% of cases, Poltergeists become extraordinarily active and aggressive.

Theories

 * They are souls rejected by The Archangel (or souls that somehow rejected the Archangel).
 * They are psychic residue left by someone with a strong connection to a particular place.
 * They are manifestations of beings who live in other realities, manipulating matter on a different reality as a result of Dimensional Bleeding.