 Item number SCP-731 Object Class, Euclid Special Containment Procedures A system of decommissioned utility tunnels at Site-9 was sealed off and converted into a mock sewer system covering an area approximating six city blocks, with 17 street-level access points sized to fit SCP-731-1. D-Class personnel are sent to check the manhole covers, every one to two weeks, to ensure that SCP-731-1 does not attempt to stray farther afield. All other horizontal access hatches or aperture covers within a five-kilometer radius have been sealed or retrofitted to a form factor incompatible with SCP-731-1. The mock sewer system is to be kept impenetrable to the entrance or exit of any vermin or other small creatures. A mixture of simulated wastewater and refuse is to be cycled intermittently through the system via pumps. Human access to the sub-street-level system is via decontamination locks. The sub-street level is not considered hazardous, but care must be taken against any unexpected tricks or traps that may be set by the SCP-731-2 contained within. SCP-731-2 is classified as safe. SCP-731-1 is a steel disc 63 cm in diameter, approximately 3 cm thick, weighing 55 kg. On its upper side, it resembles an ordinary manhole cover with two apertures for the insertion of lifting picks and a traction pattern embossed in its surface that resembles a maze. A logo in the center consists of two short bars with arcs, extending from their midsections. The appearance of the cover does not correspond to any known utility system or manufacturer, though the logo could potentially represent or. On the underside of the disc is an intricate geometric pattern of etched curves, whose purpose or meaning is unclear. The existence of an SCP candidate was first suspected in downtown when data mining revealed the suspicious pattern of unexplained missing persons. The pattern stretched back at least 50 years, prior to which time inadequate records were kept to track the disappearances with certainty. The underlying pattern to the disappearances was matched to the sewers and utility tunnels of the city. The last known location of disappeared victims was always in the immediate vicinity of an access manhole. Foundation teams searching the tunnels eventually discovered the unusual patterning on SCP-731-1's underside, but by the time they returned with a containment vehicle, SCP-731-1 had transposed itself with another manhole cover, somewhere else in the city. SCP-731-1 was ultimately cornered, after a campaign was launched to weld down every manhole cover in the city, under the guise of anti-terrorism measures. Restricting SCP-731-1's mobility, to the point where its only option was to transpose into a manhole that had been prepared for rapid removal and transport. SCP-731-1 appears to act as a sort of roving ambush predator. Its senses are unknown, but apparently very acute. When it is stepped on by a lone human who is not being observed by anyone else, the victim appears to fall down the manhole, in actuality being sucked into the solid surface of SCP-731-1. Simultaneously, a single large Norway rat, Rattus Norvegicus, hereafter designated SCP-731-2, is disgorged from the underside of the cover to fall into the tunnel below. It is thought that SCP-731-1 somehow converts its victim into this rat. The maximum range over which SCP-731-1 is able to transpose itself with compatible manholes, or whether it is possible for it to jump to another network of utility tunnels not directly connected to its current home, is not known. The frequency of its spontaneous jumps increases the longer it goes without performing a mission, possibly with the goal of finding better hunting grounds. It is therefore hoped that by allowing it to capture and convert a D-class personnel on a regular basis, it can be kept satiated and will remain within the foe city where it is currently contained. Addendum SCP-731-2 The rats, produced by SCP-731, appear physiologically normal at first examination. However, evidence suggests that they possess an unusually high level of intelligence, and that they may retain specific knowledge and or memories possessed by the humans they were created from. SCP-731-2 have proven extremely adept at overcoming puzzles and other challenges, and are only rarely fooled by conventional rat traps. SCP-731-2 avoid human contact wherever possible, and their endocrine responses suggest they are universally terrified by the presence of humans. When kept under observation in a laboratory setting, this fear appears to override much or all of their higher brain functions, such as they may be, causing their behavior to appear similar to a normal rat. This makes confirmation of their intellectual capabilities under controlled conditions difficult. Concealed cameras and microphones were hidden in the tunnels of the containment facility to observe converted rats in their natural environment. When unaware that they are being observed, SCP-731-2 are highly social and appear to attempt to communicate in complex ways. Since the rats are far easier to contain than the teleporting manhole cover that produced them, this study has been judged of low risk, and SCP-731-2 have not been subject to routine extermination. When normal rats are introduced into cages with SCP-731-2, SCP-731-2 tend to be timid and exhibit submissive behavior towards their wild cousins. The normal rats do not appear to consider SCP-731-2 unusual. Mating behavior has been observed, but it does not appear that these superficially similar species are interfertal. It is not yet known whether SCP-731-2 are fertile at all. SCP-731-2 appear to have a longer lifespan and lower metabolic rate than natural rats, with a correspondingly reduced fecundity. This further reduces the potential risk of SCP-731-1's progeny escaping into the wild, though a population may still exist in... For selected experiments, see Experiment Log 731. Experiment Log 731. Experiment 731-12. An attempt was made to drill into SCP-731-1 to recover samples and assess its durability. SCP-731-1 immediately transposed to the farthest available manhole in the containment network, preventing any damage. A repeat attempt while leaving no local manholes available for retreat is on hold, pending the development of an easier way to track and recapture SCP-731-1 than was employed initially. Experiment 731-19. A tracking device was fastened to SCP-731-1 via a cable, looped through the object's two pick-holes. SCP-731-1 transposed to a new location within containment. As soon as the technicians who had performed the task left the area, the cable was severed and both pieces remained at the original location. It is likely that any similar attempt to tie down SCP-731-1 through its pick-holes would prove unsuccessful. Experiment 731-40. An ordinary domesticated cat was introduced to the street level of SCP-731 containment. When it eventually wandered onto SCP-731-1's surface, it fell through in the same manner as a human subject, but no rat was disgorged from the underside. It appears that the cat was destroyed. Experiment 731-87. An ordinary domesticated cat, experienced in rat control, was introduced to the sub-street level of SCP-731 containment. The SCP-731-2 rats populating that level appeared terrified by the cat and fled in a normal manner, and the cat succeeded in catching and killing two of them. However, one hour and 45 minutes into the experiment, the cat's feet were injured while pursuing a third. The cat was recovered, and numerous metal slivers were found in its pads. It appears that the rats had nod these off of the interior of a degraded metal pipe and had deployed them as a field of primitive caltrops, with the fleeing rat luring the cat while itself navigating a pre-designated safe path. Experiment 731-92. A ferret was introduced into the sub-street level of SCP-731 containment. The rat's anti-cat caltrop fields proved ineffective against this more agile foe, but it appears they were already prepared for this eventuality. The ferret succeeded in killing one rat, and then was itself fatally wounded when it pursued a second into a confined tunnel. The rats had managed to find and sharpen a nail, rigging it to rise up from the ground at an angle when a platform immediately beyond it was stepped on, to impale a pursuer. Further predator introduction experiments have been suspended, as it is not clear what more can be learned from this. Experiment 731-115. A pad of paper and a set of pencil graphites mounted on short plastic dowels suitable for gripping a rat's jaws were introduced in the sub-street tunnel system of SCP-731 containment. While the presence of these items was immediately noticed by several of the rats, and word apparently spread quickly through the system, it took over three hours for the rats to emerge from hiding and cautiously approach. Although they did not appear to be aware of the specific locations of the hidden surveillance cameras, their behavior seemed to suggest that they were aware that they were being watched, apparently by deduction. A heated, squeaking argument appeared to ensue among several of the rats, involving both conventional rodentine dominance and submission displays, and recognizably human-like four-paw gestures. Finally, one of the larger rats tore a sheet from the pad, and used a graphite to write, F**K YOU, in shaky but readable English. The rats then absconded with the graphites and the rest of the pad, succeeding in hiding them somewhere in the system not covered by surveillance. It is recommended that the surveillance network be reviewed, and these previously unknown holes in its coverage filled. Lesson complete. If you missed the previous orientation, go watch SCP-730, De-Cerebrating Plague, right now, or for the complete course, watch this playlist.