Special Containment Procedures
SCP-513 is to be suspended in a one cubic meter block of gelatin and contained within a soundproofed, climate-controlled cell. The gelatin must be inspected daily for any degradation or loss of integrity. An emergency inspection will be carried out immediately following any earthquake, explosion, or sonic event grade 2 or higher. Personnel performing the inspection are to wear earplugs and active noise-canceling earmuffs at all times while inside SCP-513’s cell.
If the gelatin cube shows any signs of degradation (such as rips, tears, splits, liquefaction, or mold), SCP-513 is to be immediately removed and suspended within a replacement cube by a team of surgically deafened Class-D personnel. No other personnel are to enter the cell during this procedure.
Any sentient beings exposed to SCP-513 are to be monitored by at least two security personnel at all times. Under absolutely no circumstances may exposure victims be administered sedatives or allowed to fall unconscious. Any victim who does fall unconscious is to be terminated immediately.
Class-D personnel are to be terminated at the first sign of mental degradation. All other exposure victims may be terminated at their request.
If possible, SCP-513-1 is to be apprehended on sight.
Physically, SCP-513 is an unremarkable, rusty cowbell. No marks or engravings are visible on its surface due to the large amount of corrosion. Attempts to remove the rust chemically or mechanically have had no success.
SCP-513 was recovered by Agent ██████ while carrying out Containment Reestablishment Procedure Mu at Site-██. SCP-513’s clapper was firmly held in place by several strips of duct tape. A single scrap of paper was found along with SCP-513 (see Addendum).
Any noise produced by SCP-513 immediately induces strong anxiety in all sentient beings who hear it, regardless of their previous mental status. Exposure victims report feelings of being watched by an unseen entity and present elevated heart rates and blood pressure. Roughly one hour after exposure, exposure victims begin to catch glimpses of SCP-513-1 when opening doors, walking past mirrors, turning their heads, or performing any other actions that result in a sudden change in visual perception. Upon being sighted, SCP-513-1 reportedly turns away and runs out of view before disappearing without a trace. Questioning of bystanders indicates that SCP-513-1 is invisible to those who have not been exposed to SCP-513.
Sightings of SCP-513-1 reoccur every 14 to 237 minutes. This “stalking” behavior inevitably causes extreme sleep deprivation, as victims are frequently disturbed by SCP-513-1’s presence in their quarters. Victims able to fall asleep before SCP-513-1's appearance report being physically assaulted by it. Upon the victim's awakening, SCP-513-1 flees as usual (see Experiment Log 513). This sleep deprivation, along with the mental stress caused by SCP-513-1's behavior, invariably induces paranoia, aggression, hypervigilance, and depression. All test cases but one have ended with the test subject’s suicide.
Descriptions of SCP-513-1's appearance are largely unreliable. Test subjects are unable to provide complete accounts of sightings due to their exhaustion, degraded mental health, and disruptive hypervigilance. However, all interrogations thus far indicate that SCP-513-1 is a tall, emaciated humanoid with abnormally large hands.
Addendum: Text recovered from Site-██
You’ve seen it. Now he can hear you.
You’ve touched it. Now he can see you.
Never ring it. If you hear it, he can touch you.