The origin is still unknown. Made of concrete and rebar. SCP-173 is animated and extremely hostile. The object cannot move at a time when it is within the line of sight. When working with him, eye contact should never be broken. Personnel assigned to enter the container warn each other before blinking. The target attacks by breaking the neck at the base of the skull. Often leaves a reddish-brown substance on the floor in the holding cell. Can't speak or engage in any communication.