Every 8 months SCP-2378 undergoes a transition period, where it 
becomes "linked" to a new individual’. At this point, the interior 
layout, and physiological conditions within SCP-2378 are altered, 
rendering previous navigational charting useless. Anyone within the 
structure during a transition period may experience relocation into 
non-navigable tissues, or outright dematerialization. Newly linked 
individuals are tracked and observed by foundation undercover 


operatives for anomalous activity. Please see Observation Log 
SCP-2378-12 for a list of notable linked individuals. 


SCP-2378 has 2 openings at ground level, each 5 meters wide, 
oriented due north and due south. Caverns directly attached to the 
opening are sloped downhill, and once every 3 months the openings 
will contract, and a brown viscous fluid will wash out onto the forest 
floor, before promptly dematerializing. These openings, as far as 
current exploration and research efforts have determined, are not 
directly connected, and in fact may be mirror images of each other. 


From these openings, four definitive geographical/anatomical 
regions have been explored and described. These regions, 
SCP-2378-A, B, C, and D are described below. 


Show information on SCP-2378-A 


SCP-2378-A are a collection of intertwining caverns and 
tunnels, 50-70 km in length and 100m to 1km in width. 
Tunnels descend at a shallow gradient, possibly even 
stretching beyond the 3km radius of the surface 
structure. A regions are analogous in structure and 
composition to the human small and large intestines, and 
can be visibly segmented into 3 distinct regions. 


Segment 1 is composed of large muscular cells similar in 
structure and function to human sarcomeres. Every 3 
months, these cells contract, allowing large amounts of 
fluid to seep from the floor. 


Segment 2 is 1-5 km in length, with the floors, walls, and 
ceilings being composed of large porous mucousal 
membranes. Humidity and ground moisture increase the 
further one progresses into the segment. Large protein 
structures, termed SCP-2378-1, analogous in structural 
composition to human antibodies? may be encountered 
at this point. Structure, size, and amino acid composition 
of said structures may vary based on the current link. 
Physical contact should be avoided. 


Segment 3 regions are 5-60km in length, surfaces are 


moist mucousal membranes composed of thick bulbous 
structures analogous to villi and microvilli in human small 
intestines, and are susceptible to irritation. This segment 
contains large pools, lakes, and even rivers of liquid bile 
salts, as well as rock formations composed of important 
bio-organic nutrients. A number of anomalous 
organisms, considered separate and distinct from the 
structure, occupy these environments as detailed below. 


¢ SCP-_ - Clostridium difficile, 40 cm x 100 cm, 
which buds endospores in a manner similar to 
yeast. 

* SCP-_ - Faecalibacterium prausnitzii, 30 cm by 
50 cm, which produces ethyl alcohol, a number of 
previously artificially produced fatty acids and 
lipids, and Lisdexamfetamine from normal dietary 
fibers. 

* SCP-  - Members of the Rotavirus family, 20 cm 
in diameter, which float through the air and seem 
to exhibit Brownian motion. Researchers should 
avoid periods of high densities. 

* SCP- -"T" bacteriophages, 30 cm in height, 

specific to Escherichia coli. Manifestations exhibit 

behavior similar to that of Canis familiaris. 

SCP-2946 - A large-scale manifestation of 

Escherichia coll. 

SCP- -A large-scale manifestation of any 

member of the Taenia genus. 


Each of these organisms is capable of sensing large 
concentrations of sugar, even in a human host, and will 
engage in aggressive predatory behavior to secure these 
sources. 


SCP-2378-A is the most variable of the four currently 
explored anatomical regions. During transition periods, 
entire segments of A regions may disappear or appear. 
The slopes, flora composition, and intersection points 
along its length may shift based on a large number of 
poorly understood factors. In some cases, new, 


previously unidentified tissues may attach close to the 
lateral end of A. All exploration forays into these regions 
have been met with conditions requiring at least BSL-3 
equipment, and were subsequently scrapped in favor of 
further exploring existing structures. 


Portions of A closer to the entrance of the tunnels are 
usually used as staging points for exploration into B and 
C regions, based primarily on the rigidity of the walls, 
and the proximity of an escape route. SCP-2378-A is 
connected to B and C regions via intersections along its 
length, and connected to the D region via a single 
opening at its lateral end. 


Show information on SCP-2378-B 


SCP-2378-B are thick-walled, branching, 5 meter wide 
tunnels, analogous to human blood vessels. Tunnels are 
filled with either a viscous maroon or amber colored fluid 
compositionally similar to human plasma. Fluid flows 
along a pulse-generated$ current. The source of this 
current has yet to be located. In regions of intersection, 
the walls of these tunnels are more porous, allowing 
nutrients and oxygen to flow in and out. In non- 
intersecting sections of SCP-2378-B, surfaces are lined 
with tightly interlocked sheaths of cells, and may be 
anywhere from 50 cm to 10 m thick. B regions interact 
closely with both A and C regions, transporting freshly 
broken down nutrients from A to other anatomical 
regions, while carrying antigens and foreign material to C 
interfaces for processing. 


Several sub-entities occupy SCP-2378-B, including -1, 
-2, -3, and -4 instances. These often travel back and 
forth to C regions. -B tunnels contain high frequencies of 
SCP-2378-1 instances4. 


SCP-2378-2 are large donut shaped cell structures, 
lacking a nucleus, with high concentrations of 
hemoglobin. -2 instances are completely harmless, and 
serve as transport vessels for nutrients and oxygen. 


SCP-2378-3 are a group of entities which resemble 
human immune cells, 1.2-3 m in diameter, from both the 
innate and adaptive immune responses, which occupy 
both B and C regions. Physical contact with these 
entities should be minimized? as it will initiate non- 
specific aggressive responses. Physical contact with -3 
instances while bound by a -1 instance should be 
avoided, due to the high probability of a Class 2 event 
(See exploration log E-2378-3). A large physical gap 
should be maintained between personnel and 
SCP-2378-4 instances; physical interaction should not 
occur under any circumstances (See Addendum-2 and 
Exploration log E-2378-4). 


B regions are also occupied by a number of anomalous 
organisms and cells which are considered separate from 
the structure itself. These entities are detailed briefly 
below: 


* SCP-  - Schistosoma mansoni 2m in length®. 
Often attracts SCP-2378-3 instances and causes 
severe damage to walls in B regions. 

* SCP- - Mycobacterium leprae, 10 cm x 20 cm, 
found inside of SCP-2378-3 instances clustered 
together. Pink in pigmentation. 

* SCP- -A previously undescribed member of the 
Filoviridae family of filamentous hemorrhagic fever 
viruses, 2m x 10 mm. 


Show information on SCP-2378-C 


SCP-2378-C are a series of branching, 5 meters wide, 
tunnels connected to large ovoid caverns’ analogous to 
the human lymph system. Tunnel surfaces are lined with 
loosely interlocked cells similar to intersecting areas of B 
regions, and are filled with either clear, white, or yellow 
pigmented fluid depending on the orientation and 
proximity of the nearest ovoid chamber. The caverns are 
occupied by a large number of densely packed 
SCP-2378-3 instances. 


C regions serve as an interchange, allowing passage of 
-3 instances into other geographical regions, as well as 
filtering of foreign substances into the tunnels for antigen 
processing. Large concentrations of adaptive immune 
instances, analogous to the variety of T-cells and B-cells, 
make traversing the tunnels, and especially the caverns 
particularly perilous’. Any specific receptor binding by a 
T or B cell instance may initiate a severe irritation event, 
thus physical contact should be kept minimal, if possible. 
Due to the high variability between linked individuals’ 
immune systems, it is recommended that exploration 
requests be subject to immunization and genetic reviews 
of the current link. 


In addition to -3 instances, like other sections of 
SCP-2378, C regions have a number of separate 
anomalous organisms. These anomalous organisms 
often directly infect, attack or are directly attacked by -3 
instances9. 


* SCP- -A Macrophage, 3 m in diameter, 
possessing a long scaled tail. Exhibits behavior 
similar to that of most small lizards. 

* SCP-  -B lymphocytes, 1 m in diameter, bearing 
both B and T cell receptors. Exhibits behavior 
similar to that of Felis catus. 

* SCP- - Various T-lymphocytes, 1 m- 2 min 
diameter, exhibiting auditory calls matching those 
of Bos taurus, and engaging in behavioral patterns 
typical of members of Artiodactyla. 

* SCP-_ - Yersinia Pestis, 15 cm x 40 cm which 
[[REDACTED]]. 


Show information on SCP-2378-D 


SCP-2378-D are two, single, 1 km wide and 3 km high 
caverns connected to each respective A region by a3 
meter wide valve sphincter and a single 3 meter wide 
sphincter at the "top" of the cavern. -D regions are 
morphologically similar to the human stomach. Caverns 
are lined by thick mucousal layers with a large number of 


hydrochloric acid pumps. The sphincter attached to A 
opens briefly for 10 minutes, at intervals of 30 minutes. 
When it opens, a mixture of highly concentrated 
hydrochloric acid and large, partially dissolved 
manifestations of various foods, depending on the 
current link, will flood into SCP-2378-A. The sphincter at 
the top of the cavern has, to date, shown no discernible 
opening pattern, and when it does open, allows the 
passage of previously mentioned food items or liquid. All 
food and liquid items which enter D regions correspond 
to items consumed by linked individuals at noted times of 
observation. Acidity, and mucousal integrity vary from 
link to link, and in some cases may causes severe 
irritation events. 


Each SCP-2378-D is located roughly 30 km's below the 
surface structure. Due to the highly corrosive nature of 
both D regions, human travel is neither feasible nor 
possible, thus a corrosion resistant remote controlled 
vehicle is required for exploration. To date, no separate 
anomalous entities have been observed in either D 
region. 


SCP-2378's interior is quite susceptible to irritation, via humans or 
one of the many anomalous entities that occupy its tissues. Normal 
irritation events are dubbed "Class 1" events. During a Class 1 
event, the structure will usually exhibit a number of responses. 


* Sudden and violent shaking, which may amplify the irritation 
event by tearing/bursting some B regions. 

¢ Excretion of unpleasantly odorous fluid from the exterior 
surface, often laced with high amounts of urea 

¢ Deployment of large quantities of -1 and -3 instances into B 
regions. 

* Contractions in A regions, inducing a flood of waste and 
incomplete digestion products through either exterior 
openings. 

* Contractive expulsion of fluid from D regions through the top 
sphincter. 


Class 1 events also generate responses in the linked individual, 


NOTE: MUNDANE ITEMS OMITTED, FULL RECORD AVAILABLE 
ON CALL#0098-89-DDA 


Money Entered: 500 Yen 

SCP-261 Powered or Unpowered: Powered 

Item Description: “Dark Surprise Gum” - Small cellophane packet, 
Japanese kanji text, but with a significant amount of Japanese 
internet slang terms, produced by “Hello Okashi” Package depicts a 
ghostly, long-haired bleeding woman reaching out from a school 
locker. Opening the package revealed three smaller individually 
wrapped wafers, the approximate dimensions of a standard playing 
card. Unwrapping one of the packages revealed a thin wafer of 
black chewing gum, while the inside of the wrapper was covered 
with kanji, and a depiction of a feral dog with a distorted, human-like 
face. The text related a truncated and gruesome version of the 
“Jinmenken” or human-faced dog legend. The gum itself had a mild 
anise flavor, and was described as rather gritty and unpleasant by 
Dr. Allok, the consumer. 


Approximately one hour after consuming the gum, Dr. Allok began to 
behave erratically. Over a space of ten minutes, he became 
increasingly agitated, stating that he saw movement from the corner 
of his eye, heard odd and unsettling sounds, and felt intensely 
observed. At the end of the ten minutes, Dr. Allok abruptly 
screamed, recoiled from an unseen force, and fell to the ground. 
After recovery, and a in-depth sweep by security, Dr. Allok stated 
that a warped, decayed human-faced dog had suddenly pushed 
open the test chamber door, howled or screamed, and then charged 
at him. No other members of staff or security observed this, and no 
sensors or security alarms had been tripped. After recovery, there 
was no additional effect. 


It has been determined that the gum causes a timed hallucination 
related to the story on the wrapper. Approximately half of the gum 
wafer is required to trigger the effect, and judging by perforations 
along the center of the wafer, the gum is intended to be shared. How 
such a directed and structured hallucination is caused is still being 
reviewed, however it is not purely a chemical process, and there 
appear to be no lingering effects beyond mild paranoia, which varies 
by individual. Additional wafers relate stories of an unknown, 


including the following: 


¢ Scratching, pulling, or biting of limbs and extremities in a 
detrimental manner 

Heightened perspiration 

¢ Development of fever, swelling, and congestion 

Diarrhea, possibly with blood depending on the severity of 
irritation 

¢ Emesis and acid reflux 


In rare instances, a Class 2 event may occur. Class 2 events are 
triggered by SCP-2378-3, -4 instances, or severe illness/physical 
trauma in the linked individual. These phenomena include the same 
signatory responses as a regular event, but also incur active 
SCP-2378-3 and -4 into A regions, irreparable damage to 
anatomical segments, and severe tissue damage/failure as well as 
internal bleeding in linked subjects. It is currently not known how the 
expiration of a linked individual might impact the anomaly0. 


Discovery: SCP-2378 was first discovered by Foundation 
engineering teams surveying a large portion of unoccupied, recently 
purchased land on July 5th, 1983 near , Alabama"!. 
Appropriation of local historical records indicate that the structure 
may have first emerged sometime following the San Francisco 
Earthquake in 1906, when a small quake measuring at magnitude 3 
on the Richter scale was detected in the surrounding area. 


Initial genetic testing revealed that all tissue components of the 
structure corresponded genomically with current Foundation 
employee, Agent Sam . Agent had recently been diagnosed 
with Stage 3 colon cancer. Seismic events, and a number of severe 
irritation events over the course of the previous year prompted 
inquiry'2. Exploration of A-regions, at the time, maintained 
congruence with this diagnosis, with large numbers of quickly 
dividing cells spreading about the segment walls, and forming large 
atypical lumps. Agent underwent therapeutic surgery on July 
3rd 1997, followed by chemotherapy, resulting in 13 irritation events, 
and a small-scale seismic quake inflicting worth of damage on 
the nearby town. 


Further exploration lead to the discovery of attached anatomical