Deadites

Deadites are reanimated corpse-like Monsters kept in The Facility. They were listed on the white board and bet on by the Story Department. Later, they are seen during the System Purge.

Physical Descriptions and Attributes
According to The Evil Dead franchise, Deadites are the bodies of human beings who have been possessed and then reanimated by demonic energies or evil spirits to cause chaos and torment the living. After a spirit has possessed a corpse, its physical attributes and characteristics are the same to that of the person who had passed away. However, dark magic used by the spirit causes the body to change in certain significant ways, such as the teeth growing sharper, eyes turning pale, and the skin decaying. The longer someone remains possessed by a demonic spirit as a Deadite, the more hideous they are in appearance. It is never revealed whether the Deadites in The Cabin in the Woods function in this way as well.

It is unknown what item summons them. However, there are many possible ideas, such as reading from the Necronomicon, a dark magic-based ritual, tampering with items of the deceased, and so on.

Appearances
The first time we see a Deadite is in a long hallway, where it first runs past the frightened Facility workers,grabs a male staff member while pushing a female staff member into a wall, while a Wraith passes over head. Another Deadite is seen grabbing a worker and throwing him over the railing straight into the mouth of the Giant Snake.

Inspiration
The Deadites are a direct reference to the Deadites of the Evil Dead series. It is possible the Deadites seen in this film were a hint specifically towards the 2013 Evil Dead remake/reboot/continuation.

Trivia

 * The Deadites are very similar to The Reanimated monsters, as they are both humans brought back from the dead to cause havoc and fear upon the living. It is unknown if the inspiration for both of these categories of monsters is the same or if they come from the same background.