The Threshold opened into the Backrooms
A schematic labeling the Threshold as a "Null Zone"
or Project KV31 (also known as the Threshold, The Machine, or The Door) is a device used by the Async Research Institute as a doorway between the real world and the Backrooms (Also known as Hallways or The Complex). The device functions by making use of the Backroom's Null Zones, which are theorized by Async to be natural connections between the Backrooms and reality.
History[]
A very early prototype was tested in the Oak Ridge National laboratory on May 10th, 1982 under the supervision of Philip R. Heyman. The machine consisted of eight electromagnetic field generators directed on a single point. A small metal ball was held in the middle, and after the machine started, a bright light surrounded the ball and the ball disappeared as it was sent to the Backrooms. After that initial success, the project was taken over by Async and scaled up to the size of a doorway. The Threshold was finally opened on the sixth test on October 17th, 1989, due to the 1989 Loma Prieta earthquake, the Threshold opened causing the lab to crumble. After the Threshold was opened, thousands of people fell into the Backrooms.
While the current machine is still in operation after opening the Threshold, Async had plans to construct more versions that would've had an even larger opening. It is unknown if any further LPMDS were constructed as of this time.