an illusion that it is morning, prompting people to get up, shower, eat breakfast etc. then leave for work or school, but when they exit their homes, they walk into the middle of the night, or sometimes something worse.
An art gallery, containing surreal art on the first floor, and a gallery of art made of human parts on the second. Every so often new pieces will appear on the second floor. Potentially, when people in the near by area go missing. (shaky at best)
a humanoid monster that is harmless in the dark but becomes more visible/fast/hostile with light. (abandoned)
radio frequency, containing broadcast of singing that resembles (a) human voice(s) but at an impossibly low register. Might be traced back to the bottom of an ocean (thinking northern russia). Might resemble an ancient language (maybe from a different geographic area?), and potentially changes preceding events of great worldly significance (disasters, collapses). (last part unoriginal, but could be replaced with something more interesting)