Addendum 1538-2 - Summary of Expedition 1538-1: Following a six-month period after the recovery of Note 15, researchers determined that no further notes were likely to be forthcoming. Initial investigation of the GPS coordinates contained in Note 4 revealed the presence of a small, unmapped entrance to the Sogsagim cave system. On ██/██/2010, Foundation personnel organized an exploratory party to investigate any accessible portions of the cave system and document any findings.
An eight-person group consisting of three researchers, three security personnel and two D-Class test subjects were dispatched to Hallasan National Park. D-Class subjects were equipped with ropes, helmets, flashlights, and associated spelunking gear, as well as a helmet-mounted video camera, a cable relay for audio communication and two days' worth of emergency provisions. Researchers established a small observation outpost at the cave entrance while security personnel established a perimeter and failsafe devices at the entry point. At 0615 hours on ██/██/2010, D-Class subjects commenced exploration.
Initial observations were consistent with a primary cave or lava tube structure, similar to previously documented portions of the Sogsagim complex. The initial 200 m of the passage consisted of a tubular, approximately 3 m diameter passageway proceeding in a westerly direction until narrowing considerably and sloping sharply downward. The passageway was lined with an unidentifiable dark red slurry, and featured a considerable amount of arthropod activity as unidentified species of beetles, centipedes, and spiders were observed in substantial quantities at its entrance. D-88127 (equipped with a video camera) crawled first into the passage, followed by D-49213.
Subjects crawled through this portion of the cave for three hours, at times having to assume a completely prone position due to extremely narrow stretches. After descending an estimated 85 m during this time, the passageway opened into a spacious chamber featuring numerous speleothems (mostly pillars and dripstone), typical of nearby cave formations. Subjects observed, however, that the floor of the chamber consisted of polished black marble tile, in the manner of a constructed dwelling. No other signs of human habitation or artifice were present. Subjects continued traveling for approximately 30 m in a southeasterly direction until encountering a .75 m diameter hole in the chamber floor. After searching for alternate routes outside of the chamber and finding none, subjects established an anchor point at a nearby pillar, attached a rope and descended into the hole.
Subjects rappelled into a shaft with an estimated depth of 25 m, terminating in a small chamber. Upon reaching the floor of the chamber, subjects documented their surroundings, noting that the walls and floor were coated with the same slurry as the initial passageway. In the center of the chamber, subjects discovered what appeared to be a twin-screw extruder machine with an integrated computer terminal, such as that seemingly described in the SCP-1538 narrative (described in later reports as SCP-1538-1). SCP-1538-1 was wired to a series of automotive batteries, which served as an apparent improvised power source. No other artificial structures appeared to be present in the chamber.
Upon instructions from researchers, D-49213 approached the computer terminal and activated SCP-1538-1. D-88127 recorded video data of the encounter. The following is a transcript of the subsequent sequence of events:
D-49213 powers on SCP-1538-1. A startup sequence displays on the integrated monitor, consistent with activity described in the SCP-1538 narrative. A prompt reading "input command" appears on the screen.
D-49213: Initiation confirmed. What do you want me to do next?
Researcher Eng: (via D-49213's telecom link) Please input "initiate operation 15 mode 3" into the terminal.
D-49213: Copy.
D-49213 enters the command as instructed. After twenty seconds, a response appears on the screen, reading "unrecognized operator present", followed by a second message reading "requested data not found".
D-49213: What now?
Researcher Eng: (unintelligible dialogue from multiple staff in background) Um, stand by…(additional background dialogue from multiple staff) wait and see if it returns to the "input command" prompt.
D-49213: It's making some sort of grinding noise now.
SCP-1538-1 commences mechanical operation. A message on the monitor appears reading "initiating Sequence 4".
D-49213: It's doing something now, things are moving. There's something coming out of it.
Researcher Eng: D-88127, I want video of the output port.
D-88127 moves the camera towards the end of SCP-1538-1. As the camera focuses closely, SCP-1538-1 is shown producing a steady stream of a substance resembling the dark red slurry documented previously in the cavern at a rapid rate. The substance appears to be intermixed with teeth, bone fragments, and scraps of epidermal tissue.
D-88127: What is that?
Researcher Eng: Please continue the video feed.
SCP-1538-1 continues to produce a steady supply of slurry despite lack of visible input. As the mound of slurry approaches a height of 2 m, movement becomes apparent within it.
D-49213: There's something moving around in there, command.
Researcher Eng: Maintain video contact.
Movement continues within the SCP-1538-1 slurry pile. After 45 seconds of additional observation, a pseudopod-like structure emerges from the center of the slurry pile. At the end of the structure is what appears to be a skinned human face.
D-88127: Shit! Shit!
Researcher Eng: Keep the camera on it, 88127.
The pseudopod extends directly upwards to a height of approximately 4 m before beginning to move towards D-88127.
D-49213 Get the fuck out of here!
Video contact is lost as the camera is dropped to the ground and subjects flee. The sounds of a rope ascender being attached are audible, as well as unintelligible screaming from D-88127 and the sounds of fabric ripping and an unidentified liquid spilling onto the floor.
Neither subject responded to repeated orders and attempts at communication over the telecom link after loss of the video feed, although what is presumed to be D-49213's labored breathing and the sound of a rope ascender were heard constantly for the next ten minutes.
At 1327 hours, D-49213 confirmed that he reached the marble tile chamber above SCP-1538-1. Faint, unintelligible screaming was heard in the background of D-49213's communications. Researchers repeatedly asked D-49213 for an explanation of events after loss of the video feed; no answers were forthcoming.
D-49213, against direct orders from researchers, proceeded back through the passageway towards the cave entrance. At 1441 hours, D-49213 reported unidentified noises in the passageway behind him. Due to the tight confines of the passageway, D-49213 was unable to achieve visual confirmation of the source of the noises, but repeatedly informed researchers that he was being pursued.
Researcher Eng conferred with staff and contacted Research Director Trilling at 1450 hours. Upon Research Director Trilling's orders to activate failsafe measures, security staff remotely detonated explosives at the cave entrance, collapsing the entryway and closing the passageway off to all access.
All audio contact with D-49213 was lost at 1455 hours.
