The stairwell of the "Qiyuan" apartment is a non-Euclidean space, and its abnormal core is represented by the "Thirteenth Step". It does not always exist, and will only appear and "select" the target under certain conditions (such as being alone, at a certain time, with strong negative emotions, etc.). People who step on it do not simply die. Instead, he will be pulled into a "laminated space" based on the memory of the apartment and the fear of the victim, suffering both mental and physical erosion, and eventually becoming part of the staircase structure, strengthening its curse. The existence of the steps is related to a forgotten evil ritual at the beginning of the apartment's construction and the crazy obsession of the architect.
