Image taken inside the control room of the underground complex prior to the incident that turned the location into SCP-3509.

Item #: SCP-3509
Object Class: Euclid
Special Containment Procedures: An appointed team of qualified researchers are to monitor the interior of SCP-3509 at all times using its own system of cameras, microphones and speakers. The teams are to deliver provisions to its current resident through the elevator that connects SCP-3509 with the rest of the Site. It will also provide any help necessary to said resident in order to fulfill whichever task SCP-3509 demands of it. The appointed team leader will have discretionary authority over the best course of approach towards those demands.
A single Class-D personnel is required to reside inside SCP-3509 at any given time. A log of its activities is to be kept up to date by the researcher team. In case of its decease or termination, another subject will be sent to occupy the vacancy.
Any Class-D assigned at SCP-3509 are required to get a perfect score in the standardized Foundation test N-051-RP, which measures the obedience and compliance of the subject. Those that also show signs of introversion or tendency to isolation will be given priority to be selected.
The newly selected Class-D personnel is to be injected with a very small explosive charge that can be remotely activated inside its thoracic chamber prior their entry. This is because the technical difficulties SCP-3509 creates to regular termination procedures once the subject is inside. The researcher team is to terminate the subject in case of disobedience or inability to comply with the order provided by SCP-3509.
In the light of the proprieties of SCP-3509, the need to rotate the Class-D personnel has been deemed unnecessary as long as the previous procedures are being followed.
Description: SCP-3509 is an underground complex with the surface of ███ square meters, being equipped with a control room, a testing chamber, living quarters and a restroom. It is located ███ meters under the bottom floor of Site-██. Its only entrance is an elevator that connects it with the observation room located at Section ██ of the site. Prior to becoming SCP-3509, this underground complex was used as a testing facility by the Foundation, where experimentation and stress tests were realized on SCP-3509 and anomalous items to observe their reactions in extreme situations.
SCP-3509 started showing anomalous effects after ██/██/2001, when the Foundation carried out inside its test chamber the failed experiment on [REDACTED], and the subsequent incident on the eight day of continuous testing. This incident caused the members of the foundation present on the complex to experience an adverse effect similar to what would later be called SCP-3509-B, with the exception of a sole survivor which became its first resident. The object experimented upon was later retrieved without apparent change on SCP-3509.
The following is a compilation of any of anomalous effects observed within SCP-3509:

SCP-3509 will constantly give commands to its resident, one at a time. To issue each order, an unidentified synthesized voice will sound through the speakers of the complex. This voice is to be referred as SCP-3509-A. Said order is observed to be seemingly random most of the times, ranging from inane to extremely hazardous to the subject. So far it has never given an order that was physically impossible to achieve. The reason why it continues to give those commands is unknown.
When an order is given, a display in the control room of the underground complex will show a countdown. The amount of time varies between a minute and a few days, with the longest time recorded being 9 days. Experimentation has shown that both the order and the countdown will be given even if no resident is currently inside SCP-3509 or if the previous inhabitant has perished.
SCP-3509 only accepts human beings as its residents and will require them to personally fulfill the order. Any other attempts by third persons outside SCP-3509 or by animals and electronic mechanisms sent inside will be ignored. A human resident may still use the help of the previous to achieve the expected result, as long as the inhabitant contributes in a significant way to the fulfillment of the order.
After an order is successfully carried out, SCP-3509 will confirm its accomplishment. It seems to be impossible to conceal the fulfillment of any command inside it regardless of the method.
The confirmation of the accomplishment will cause the countdown to be turned off and SCP-3509-A will congratulate the resident. Afterwards it will remain silent during an hour until the announcement of its next order.
Any living resident attempting to leave SCP-3509 will suffer a series of physical changes that will eventually lead to its death on the way up during the elevator ride or if they try to escape using alternative methods. The only way to survive at that point is re-entering SCP-3509 before any critical damage has been received, as it will halt the process. Those changes vary from individual to individual. Some observed instances of the process are: The creation of multiple lacerations across the body of the subject, melting of the limbs and torso, decomposition of their body as they are still alive, transformation of their living tissue into a glass-like substance, the continuous generation of metal sharpnel inside the body among others. This process will be named SCP-3509-B. The current observed radius outside SCP-3509 for this effect to take place is ██ meters.
Any living human that tries to enter SCP-3509 while it already has another resident will also be affected by SCP-3509-B. However other entities like inanimate objects, animals, plants or human corpses have been shown be able to enter and leave it completely unharmed.
If multiple subjects enter at the same time while SCP-3509 is unoccupied, all of them but one will end up suffering the effects of SCP-3509-B. The surviving subject will be physically unharmed, but will usually have to be terminated due to its highly unstable psychological state after having witnessed what happened to the other subjects. See Addendum 3509-2 for more details.
Any attempts to breach the underground complex by any other means have ended in failure. Currently no further attempts are allowed.
It has been observed that SCP-3509 has at least some degree of sentience and consciousness of itself, as shown on some logs in Addendum 3509-1.
In the only instance that the order wasn't fulfilled in time, the area of effect of SCP-3509-B began expanding at an alarming rate, affecting multiple SCP Foundation staff and Class-D present on the Site. See: Addendum 3509-2 for more details.

Besides the aforementioned, no other anomalous phenomena can be observed neither on SCP-3509 nor its resident. If the subject is complying and is able to complete tasks ordered by SCP-3509, it can survive within it during long periods of time. The record time of a resident surviving within the complex has been for 5 years. In some instances the observer team observed traces akin that of symbiotic nature between SCP-3509 and its resident, however these behaviors are not frequent as SCP-3509 usually shows very little regard to the well-being of its inhabitant.
At the current point in time it has not been fully tested what happens if an order given by SCP-3509 is disobeyed, as so far every single order it has given has been eventually carried out, albeit one outside the time limit. The Foundation's experts on theoretical approach hypothesize that due to the events surrounding the incident detailed in Addendum 3509-2, it is very likely that in the event of complete disobedience, it could indefinitely expand the area of effect of SCP-3509-B. This possible event would create uncountable losses for the Foundation and the loss of Site-██ as a whole or worse. Based on that hypothesis, O5-█ decided that an obedient approach of having expendable personnel obeying the orders that SCP-3509 gave was a safer and more cost-effective option than the possible alternative. Thus any experimentation based on disobeying the order or letting the timer run out again have been prohibited.
Addendum 3509-01:
The following is an excerpt of some of the logs kept by the researcher team tasked with SCP-3509 to be used as reference:

Day: ██/██/2002.
Resident: D-3541
Order: Jump.
Time limit: 5 hours
Result: The Class-D complied almost immediately, no assistance was required.

Day: ██/██/2002.
Resident: D-3541
Order: Study calculus for three hours straight.
Time limit: 12 hours and 20 minutes
Result: The Class-D was provided with calculus reference books and asked to study them. One member of the researcher team offered to tutor him across the site's speakers.

Day: ██/██/2002.
Resident: D-3541
Order: Rip out your nails from your left hand.
Time limit: 27 minutes.
Result: The researcher team provided a pair of pliers through the elevator. Although strongly reticent, the subject complied. Disinfectant and bandages were provided by the team after the event.

Day: ██/██/2002.
Resident: D-3541
Order: Dance the "Macarena".
Time limit: 3 hours and 1 minute.
Result: D-3541 told the researcher team that he didn't know the dance. The researcher team provided a television with a video tape that demonstrated the steps of the dance. After some attempts, D-3541 achieved to do a dance sufficient enough for the order to be deemed accomplished.

Day: ██/██/2003.
Resident: D-3557
Order: The floors are dirty, clean them.
Time limit: 5 hours and 49 minutes.
Result: The researcher team provided D-3557 with cleaning tools and it proceeded to obey the required task. The statement "The floors are dirty" was found to be most unusual, as SCP-3509-A hadn't said this kind of comment on an object before besides the congratulatory message at the fulfillment of an order.

Day: ██/██/2003.
Residents: D-3557 (Terminated), D-4286.
Order: Write a poem.
Time limit: 1 hour and 30 minutes
Result: The Class-D told to the research team that he was an illiterate. After a discussion within the team it was decided that trying to teach D-3557 how to write in that short amount of time was highly unlikely. D-3557 was terminated through the explosive charge in his chest and a replacement was sent. This replacement was tasked to write the poem once the elevator had reached its destination before exploring the rest of the complex. Once SCP-3509 congratulated her, the research team asked her to dispose of the corpse of the previous resident through the elevator.
Note: It seems that when the elevator is on the entrance of the underground complex SCP-3509 recognizes it as part of itself, allowing its resident to carry its orders inside it. This should be noted for further reference. -Team director Dr. Karam

Day: ██/██/2004.
Residents: D-4311(Terminated), Junior Researcher Garcia
Order: Smoke a cigarette.
Time limit: 1 minute.
Result: See Addendum 3509-2

Day: ██/██/2004.
Residents: Junior Researcher Garcia (Deceased), D-4371
Order: Dance claque.
Time limit: 1 day, 2 hours and 56 minutes
Result: Junior Researcher Garcia committed suicide. A new Class-D resident was sent to carry out the order as well as to retrieve the remains of the Junior Researcher.

Day: ██/██/2005.
Residents: D-4401
Order: Sing out loud the song "YMCA" by the "Village People".
Time limit: 9 hours 42 minutes.
Result: D-4401 showed signs of stage fright and told the researcher team that he was feeling too self-conscious to sing. The researcher team reasoned and encouraged it for a period of time until the Class-D suggested that he would feel more comfortable singing if the researcher team sang along with him through the speakers. After a short discussion within the team it was decided that it would be easier to humor the Class-D than preparing another substitute, and agred to the subject's request. The order was subsequently fulfilled without further incident.

Day: ██/██/2006.
Residents: D-4441
Order: Do a hundred push-ups and a hundred sit-ups.
Time limit: 24 hours.
Result: Due to the extremely poor physical state of D-4441, problems arose as it seemed to be unable to finish the regimen in time. The researcher team spent the day giving the Class-D encouragement and teaching it techniques to facilitate the fulfillment of the order. It was eventually accomplished by the 22nd hour mark with signs of exhaustion on the Class-D.

Day: ██/██/2006.
Residents: D-4441
Order: Pet a koala.
Time limit: 2 hours.
Result: One Mobile Task Force team was sent post-haste to the closest zoo to retrieve a specimen, managing its recovery and transportation within the allocated time. After the order was fulfilled, the specimen was returned and amnestics were administered to any witnesses of the operation.

Day: ██/██/2008.
Residents: D-5026
Order: Do not say "My uncle Steve has a big cow".
Time limit: 7 days 16 hours and 33 minutes
Result: This was the first instance SCP-3509 gave an order of inaction. Since it was unknown at the time how would it deem the inaction as fulfilled, any possible precautionary measures were took to ensure the safety of the Site. D-5026 was forbidden to open his mouth aside from eating and drinking until further notice. The researcher team closely monitored D-5026 at all times to ensure termination in case of any attempt at speaking. As the countdown kept descending without any indication of fulfillment of the order, an emergency meeting was called to discuss the situation with the Site Director other chief staff from the Foundation. During the last hour of the time limit an evacuation on all personnel in-site was issued, and the use of omega nuclear warheads was prepared for the worst-case scenario. At the last second, SCP-3509-A gave the announcement of order fulfilled and added that its resident could now say whatever it wanted. Once the crisis was deemed to be averted, the Foundation staff returned to their regular activities and the incident was disguised as a security drill. Afterwards, D-5026 commented how easy this order had been compared to previous ones since he didn't have any uncle called Steve.

Day: ██/██/2009.
Residents: D-5026.
Order: Repair the broken lamp.
Time limit: 6 days 3 hours and 4 minutes.
Result: D-5026 was given the materials and instructions by the team to repair the lightbulb that was accidentally shattered during the previous order of "Play racquetball by yourself for five minutes".

Day: ██/██/2009.
Residents: D-5026 (Deceased).
Order: Walk three meters on a tight rope
Time limit: 3 days 5 hours and 15 minutes.
Result: The researcher team provided the materials for the Class-D to make an improvised tight-rope inside the facility. Several attempts were made by D-5026 during the course of the first two days. At the last attempt, just as SCP-3509-A gave the congratulatory message, D-5026 slipped and hit its head on a table, causing skull fracture and internal hemorrhage. Due the inability of the researcher team to provide effective medical aid in time caused by the inherent characteristics of SCP-3509, D-5026 perished of blood loss.

Day: ██/██/2011.
Residents: D-5584.
Order: Write erotic fanfiction featuring your parents
Time limit: 7 hours and 28 minutes.
Result: At the beginning D-5584 strongly refused to comply until the research team threatened to terminate it. The audiovisual recordings showed the Class-D writing something on a piece of paper and immediately tearing it apart after SCP-3509-A gave the congratulatory announcement.

Day: ██/██/2013.
Residents: D-5584.
Order: Completely immerse yourself in sulfuric acid
Time limit: 5 days 12 hours and 1 minute.
Result: The researcher team provided a tank full of sulfuric acid through the elevator and a hazmat suit. After D-5544 had been reassured that the suit would protect him from any major burns he decided to comply. Treatment materials for second-degree chemical burns, as well as telephonic assistance on how to apply them was provided after the testing.

Day: ██/██/2013.
Residents: D-5584.
Order: Ride an elevator
Time limit: 1 day 2 hours and 3 minutes.
Result: Discussion of making D-5584 use the entrance elevator took place within the researcher team. It was ultimately decided against it for ethical reasons and instead a small mini-elevator was built and sent inside SCP-3509 to fulfill the order.

Day: ██/██/2015.
Residents: D-5584.
Order: Good job, you may now exit SCP-3509 and bring in a new test subject.
Time limit: 9 days.
Result: Permission was given at D-5584 to use the main elevator by the researcher team. This has been the only instance of someone being able to leave the underground complex without being affected by SCP-3509-B. Another Class-D was sent inside SCP-3509, which marked the order as fulfilled. Further testings showed that, barring this exception, SCP-3509-B still occurs every time anyone else tries to exit, and continues functioning as if this incident never happened. When interrogated about it, D-5584 claimed to have no knowledge why only he was allowed to leave. D-5584 has been administered Class-A amnestics and repurposed at another location.

Addendum 3509-02:
The following is a compilation of documents recording the Containment Breach caused by SCP-3509 on ██/██/2004.
Document 1: E-mail from the team director to the research team sent the day prior to the Containment Breach

FROM: Team director Dr. Karam
TO: Dr. Cobb, Dr. Zhurov, Junior Researcher Garcia, Research Assistant Tanaka.
SUBJECT: Experimentation on the behavior of SCP-3509.
A test is scheduled for tomorrow. This test is to measure how will SCP-3509 react if multiple living individuals try to enter at the same time. The test will begin immediately after the current resident fulfills any order issued by SCP-3509 after 8:30. When the order is fulfilled, the resident will be terminated and four Class-D will be sent down with the elevator simultaneously. I expect all of you to be prepared and ready to deal with any unexpected consequences.
Dr. Karam

Document 2: Excerpt of the telephonic interview with Junior Researcher Garcia, the resident at the time of SCP-3509, taken an hour after the stabilization of the Containment Breach. Recorded by Agent 58, leader of the squadron sent to investigate the current events, using the telephone situated on the researcher team's observation room.

Agent 58: Who is it?
Junior Researcher Garcia: Thank God someone picked the phone… Thank God…
Agent 58: This is Agent 58, leader of the squadron ████, who am I talking to?
Junior Researcher Garcia: I'm █████ Garcia, a junior researcher. My ID Number is ██████████.
Agent 58: From where are you calling from?
Junior Researcher Garcia: …I'm inside SCP-3509.
Agent 58: According to the information given to me, only Class-D are usually sent inside SCP-3509.
Junior Researcher Garcia: Yeah, that's… Shit!… That's usually right.
Agent 58: And how come a Junior Researcher has entered it?
Junior Researcher Garcia: Well, the incident happened and I couldn't think anything else than getting on the elevator.
Agent 58: Wait. Are you telling me that you were present during the incident?
Junior Researcher Garcia: Yes, fuck!, I was there. I am… was assigned to the researcher team for SCP-3509.
Agent 58: Hold on a minute.
[Background noises of Agent 58 speaking through a walkie-talkie.]
Agent 58: Sir, I would like to ask for your cooperation to relate your account of the events that happened today from 09:37 hours to 12:56 hours.
Junior Researcher Garcia: Well, we had this test programmed in which we were supposed to send multiple Class-D inside SCP-3509. During the test we observed that all of them but one became affected by particularly gruesome manifestations of SCP-3509-B. The, Shhh fuck it hurts! the cameras showed that the surviving Class-D ran away from the elevator once it opened its doors and sat on a corner of the control room, cradling his head and moved back and forth. Please, may I ask for some first aid supplies and painkillers? I'm hurt and I could really use them.
Agent 58: Let me consult my superiors.
[Background noises of Agent 58 speaking through a walkie-talkie.]
Agent 58: Okay, I've been granted permission to provide the required items, they will be sent by the elevator at the entrance.
Junior Researcher Garcia: Thank you. Thank you very much. Hold on still while I crawl to get them.
Agent 58: Crawl?
[No response. Thirty minutes of silence occasionally interrupted by walkie-talkie conversation sounds coming from Agent 58]
Junior Researcher Garcia: Okay, I'm back. I owe you a big one. Although I feel kind of dizzy now.
Agent 58: Please continue your report. You may rest afterwards.
Junior Researcher Garcia: Fine. Upon seeing the results of the test the team director assembled the rest of the group and we discussed whether if we should terminate the Class-D immediately or if we should wait and see if he would regain enough self-control to obey the next order. We decided on the latter to avoid wasting even more Class-D today. Then the voice spoke and… that happened.
Agent 58: What happened?
Junior Researcher Garcia: "Smoke a cigarette" the voice said, and gave a time limit of one minute. One. Freaking. Minute. The least that SCP-3509 had ever gave before were fifteen minutes! And the order that time was for the resident to scratch its nose, for crying out loud!"
Agent 58: Calm down. How did the team react?"
Junior Researcher Garcia: It was chaos. We had been instructed to not let the timer run out after all. Not until further testing could be carried out at least. Dr. Karam started yelling at the Class-D to react through the facility's speakers, but he would just not do anything but keep crying. Dr. Cobb, started yelling orders about terminating the Class-D and sending another one with some smokes and a lighter. Aki [Research Assistant Tanaka] also threw some of her own cigarettes inside of the elevator. Me, on the other hand, just stood there like an idiot… Fuck.
Agent 58: Did the countdown reach zero?
Junior Researcher Garcia: Yes.
Agent 58: Please explain what happened at that moment.
Junior Researcher Garcia: As the countdown ended the whole underground complex flashed some red lights and the surviving Class-D inside began to scream as his whole body was affected by SCP-3509-B while still being inside SCP-3509. It was different than other instances previously observed, as it went slower, and, based on my own experience, it seemed much, much more painful. It started by the plant of his feet, turning them into ashes in his case. That soon spread to his legs and lower torso. The subject could not stop screaming and we, the team, stared in terror as he twisted and turned in agony. The next thing we knew is that our own bodies started being affected by SCP-3509-B as well, despite being outside of its usual range of action. Dr. Cobb hurriedly pressed the switch to terminate the subject.
That wasn't enough to stop our own ailment though. I saw them all die, one after another. I heard screams outside the observation room, as well as someone yelling that the backup Class-D was attempting escape. It was hell. The image of Aki screaming as her skin began opening up multiple holes that showed her insides is something I don't think I will ever be able to live down.
Agent 58: Hold up, there's something that I don't understand. If you say that everyone around you died because of SCP-3509-B, how come that you are still alive?
Junior Researcher Garcia: I… don't know why. At the beginning, SCP-3509-B started wrecking my feet at the same rate as everyone else. But then, somehow, it started to consume me slower. I don't really get it myself, but I think it slowed down on me alone after Dr. Cobb terminated the Class-D for some reason. My best guess is that SCP-3509 had already selected me as its next resident by then, but that's just my hypothesis.
Agent 58: Noted. Continue.
Junior Researcher Garcia: At that moment I couldn't think of anything. I was confused and hurting. I didn't know what to do, just that I needed to stop that somehow. I acted without thinking, and using what remained of my legs I entered the elevator, pushing the button to go down.
Agent 58: So you entered there voluntarily, despite knowing the consequences?
Junior Researcher Garcia: I was desperate, okay? I realized what a blunder I had made as soon as the doors closed, and sat down as SCP-3509-B continued to consume my flesh. I knew I was gonna die there, and nothing mattered anymore. That's when I looked down and saw on the floor the cigarettes that Aki had thrown before. I think at that point I was experiencing an adrenaline rush because, despite the pain, I thought "You know what? Why not have one last smoke?". I grabbed the cigarette and started smoking it. That's when the lights flashed white and the other door to the elevator opened. I heard SCP-3509-A's voice giving the same line it says every time the order is fulfilled. However, it added at the end something that I'd never heard before, that "it would not allow for any other delays in fulfilling the order".
Agent 58: I see. Hold on one moment.
[Background noises of Agent 58 speaking through a walkie-talkie.]
Agent 58: Okay, that would be sufficient for now. My most sincere condolences for what happened to you, sir.
Junior Researcher Garcia: Don't need them. Just tell me if there are other people alive on the Site.
Agent 58: Yes. Although, some heavy losses have occurred in the closest sectors, most of the Site's personnel has survived. Regrettably, your team…
Junior Researcher Garcia: I know… Well, if that's everything I think I will rest for now, these painkillers are really kicking in.
[The synthesized voice of SCP-3509-A sounds on the receiver "Next testing procedure order: Curse out loud. Time limit: forty minutes."]
Junior Researcher Garcia: …Fuck my life.
[The synthesized voice of SCP-3509-A sounds on the receiver "Order fulfilled. Congratulations on the success of the test. A following test will be performed shortly."]
[END OF EXCERPT]

Document 3: O5-█ directive issued after the containment breach.

Due to a containment breach of SCP-3509's hazardous properties, a total of ███ members of the Foundation passed away and ████ were severely injured in an area of ████ cubic meters surrounding it. Since then it has been observed that the area of effect of SCP-3509-B has progressively gone back to its original size. Our experts have determined that if it weren't for the actions of Junior Researcher Garcia, the area of the adverse effect would have increased to undetermined lengths.
In light of these recent events, it has been decided that any experiment regarding the disobedience or reaching the time limit of the countdown of the order issued by SCP-3509 is absolutely prohibited.
O5-█

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