This short video is known only by the title 11B-X-1371, and in the short months since it appeared online, no one has been able to solve its mystery. Some think it’s an elaborate puzzle, while others think it’s a warning of some kind.

The only thing we know is that it’s scary as all hell.

Note: You can watch the full video at the end of the post. If you dare.

The video first appeared online in May when it was uploaded to YouTube. It appears to be shot in an abandoned building surrounded by thick woods.