Wraiths

The Wraiths are Monsters kept in the Facility. They are listed on the Whiteboard, but are not bet on. Only one Wraith can be seen during the System Purge.

Physical Descriptions and Attributes
As mentioned above, only one Wraith is seen throughout the entire film. It is unknown what the other Wraiths look like (if their appearance vary) or if they were not shown/created due to time and budget. However, we can gather information about the general behavior and characteristics of Wraiths by the one we see. Wraiths are ghostly figures- they appear as a blueish-grey mist or fog that has manifested itself in the physical world. When they show their faces, they appear as skulls. It seems that the Wraiths are angry or dangerous spirits that are trapped on Earth for some reason. Since they do not take on the typical form of a ghost or shadow person, they are unique in nature and this is presumably why they are kept in the Facility. The Wraith might attack and possibly kill its victims by some sort of possession, but this is not confirmed. The origins as well as who the Wraiths were in their human, past selves is unknown. Its possible but not confirmed that other Wraiths may be the Creeping Shadow and the Ghost. In the novelization of the film, a Wraith may have been the Toxic Ghostly Figure, given the mist of the Wraiths can be mistaken for fumes. When the Wraith is first seen by Marty and Dana, it first is seen in its foggy form. However when Dana gets closer, it manifests its face, screaming at her. It should be noted that, when Marty and Dana's cube begins to descend into the Facility, the Wraith screams for help and pleads for them not to go. This could be an attempt by the Wraith could lure its victims closer by posing as a trapped, frightened soul in need of help, only to later attack, as seen in the Purge when the Wraith's demeanor has changed into a vengeful, angry spirit.

The item that summons the Wraiths to the Cabin is unknown. However it could be an item connected to the deceased person that the Wraith was in its human life such as ashes contained in an urn, paintings or photographs of the deceased, or personal items of sentimental importance. A Ouija board could also summon them.

Appearances
One Wraith only appears during the whole film. The first time we see the Wraith is up close, in the scene mentioned earlier where Dana is startled by the Wraith when it manifests itself to her in its own cube. As their cube begins to go down, the Wraith pleads and screams at them not to go. The second time we see the Wraith is in the System Purge. It was released during an unknown wave, but can be seen flying down a hallway filled with panicked Facility workers and a Deadite. After it flies over, it turns left into a room that leads to a balcony. The camera follows it and we get a close-up shot of the Wraith screaming at the workers below it. As another Deadite throws a male worker over the balcony's edge to the Giant Snake, the Wraith flies past it and disappears. The Wraith is not seen again after this.

Inspiration
Wraith is a Scottish dialectal word for "ghost," or "spirit". They're said to be death omens who appear to anyone whose death is impending. More or less, the Wraith in the film is represented as an almost normal, common ghost. As such, ghost have appeared in stories since as long as the horror genre has existed.