Often hallucinations experienced by schizophrenic individuals are sudden and terrifying. One moment they'll be chatting with their best friend and the next they can't look up because said friends face has transformed into a hellish nightmare.
SCP-087 - An unlit platform staircase. Subjects report and audio recordings confirm the sound of a crying, pleading child estimated to be located approximately 200 meters below the initial platform. However, any attempts to descend the staircase have failed to bring subjects closer to the source.