Slender Man was born in 2009 in a photo-manipulation contest on the Something Awful forums. When a user quietly inserted a faceless, unnaturally tall figure in a black suit into otherwise ordinary old photographs, a story soon attached itself: that the figure stalks and abducts children. The images and short captions spread fast and grew into a shared character.
What makes Slender Man significant is that it is the first modern myth shaped by collective creation. With no fixed author and no canon, countless people fleshed out the same figure and grew it together — making it the model for a collaborative canon in which a myth grows as many hands repeat the same vocabulary.