SCP-513, or "A Cowbell", is an upcoming SCP in SCP: Containment Breach Unity Edition that will be added in an as of yet unannounced update.
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.
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 . 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.
SCP-513 is not currently in-game