"This is where He keeps the things He takes."
The Dark Place was a as of yet, non-corporal and undefined location until seen in "1813712 71922 2326916" and "A hole in the ground.". Its only given role has been as the place that RoivasSevil exists, and the place that Caught and Natalie are taken when paranormal and Slender Man activity occurs. A certain level of distortion (typically the high contrast) would seem to indicate the convergence of the Dark Place with the normal world. RoivasSevil's outlined avatar would also seem to be her projection of a physical self inside of the Dark Place, indicating that the Dark Place possess no physical attributes. However it is possible to "enter" and become lost in the Dark Place, as Caught's catatonic state during the events of "Running would seem to be the product of partially entering the Dark Place. RoivasSevil also seems to have become lost in the Dark Place after having been put there by her previous "family".
The Dark Place seems to be a distorted version of the real world. Seen in the videos is has woods, caves and altered versions of what was visible in the real world, such as the Lansing Place door. There are also many floating lights which are described as "memories". Thyodamas' Light also described many dry lake beds, monstrous beings, and cities of zombie-like entities. In the real world, what can be seen of the Dark Place is the distortion that it seems to put off, a typically high contrast, high color saturation distortion similar to what surrounds the Caught Puppets. The Dark Place also seems to be related to the small, floating points of light seen during "Out of Options". Where the Dark Place is corporal seems to be at those points where it converges with the real world; such as is seen during Natalie's assault during "Aftermath". The Dark Place also has a connection to backwardness. Both RoivasSevil and Caught have spoken backwards while inhabiting the Dark Place, and The Mirror, who is speculated as being a native of the Dark Place, speaks in a sort of backwards and reversed type speech. The Mirror may also be the 'things' that RoivasSevil cautions against when explaining that there are entities in the Dark Place that make it terribly unsafe, and from whom she must constantly hide. It has been implied by the Mirror that it is possible for common people to enter the Dark Place, but RoivasSevil has expressly forbidden the other viewers from attempting to do so.