Description: SCP-939 are endothermic, pack-based predators which display atrophy of various systems similar to troglobitic organisms. The skins of SCP-939 are highly permeable to moisture and translucent red, owing to a compound chemically similar to hemoglobin. SCP-939 average 2.2 meters tall standing upright and weigh an average of 250 kg, though weight is highly variable. Each of their four limbs end in three-fingered claws with a fourth, opposable digit, and are covered in setae which considerably augment climbing ability. Their heads are elongated, devoid of even vestigial eyes or eye sockets, and contain no brain casing. The jaws of SCP-939 are lined with red, faintly luminescent fang-like teeth, similar to those belonging to specimens of the genus Chauliodus, up to 6 cm in length, and encircled by heat-sensitive pit organs. Eye spots, sensitive to light and dark, run the length of their spined dorsal ridges. These spines may be up to 16 cm long and are believed to be sensitive to changes in air pressure and flow.

SCP-939 do not possess many vital organ systems; central and peripheral nervous systems, circulatory system, and digestive tract are all absent. SCP-939’s respiratory system is atrophied and serves no apparent purpose beyond spreading AMN-C227 (see below). SCP-939 have no apparent physiological need to feed, nor any way to digest consumed tissue. Ingested material typically accumulates in the respiratory system of SCP-939 and is regurgitated once the amount is sufficient to markedly inhibit its function. Despite the absence of many vital organ systems, SCP-939 are capable of bearing live young. See Addendum 10-16-1991.

SCP-939’s primary method of luring prey is the imitation of human speech in the voices of prior victims, though imitation of other species and active nocturnal hunts have been documented. SCP-939 vocalizations often imply significant distress; whether SCP-939 understand their vocalizations or are repeating previously heard phrases is the subject of ongoing study. How SCP-939 acquire voices is not currently understood; specimens have been documented imitating victims despite never hearing the victim speak. Analysis of SCP-939 vocalizations cannot distinguish between SCP-939 and samples of known victims’ voices. The use of biometric voice-recognition security or identification systems at any installation housing SCP-939 is strongly discouraged for this reason. Prey is usually killed with a single bite to the cranium or neck; bite forces have been measured in excess of 35 MPa.

SCP-939 exhale minute traces of an aerosolized Class C amnestic, designated AMN-C227. AMN-C227 causes temporary anterograde amnesia, inhibiting memory formation for the duration of exposure, plus an average of thirty (30) minutes. It is colorless, odorless, and tasteless with an estimated ECt50 for inhalation of 0.0015mg•min/m3. In well-ventilated or open air environments, risk of exposure to ECt50 is greatly reduced but not negligible. AMN-C227 is typically undetectable in the bloodstream sixty (60) minutes following cessation of exposure. Reported sensations of disorientation and mild hallucinations immediately following removal from environments saturated with the agent are similar to recreational use of numerous psychoactive substances and easily mistaken as such.