SCP-087-A, also known as "Mental" is a humanoid with black body and white face with cutted smile and black eyes. His origin is unknown, he says "No.", "Don't look at me!" and "Behind you.".
He appears at random time and disappears at after few seconds. Before he disappears, he follows the victim and tries to murder him. SCP-087-A can sometimes go up stairs and vanish immediately.