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SCP-666-EX during experimentation at the Los Alamos Laboratory.

Item #: SCP-666-EX

Object Class: Explained

Special Containment Procedures: Relevant parties have been informed SCP-666-EX has been melted down for its plutonium. The object itself has been secured in a standard nuclear-certified containment chamber by the Department of Nuclear Studies1.

As the object has been reclassified to Explained, no further procedures for its containment have been deemed necessary.

Description: SCP-666-EX is a plutonium device designed as the core for the third atomic bomb intended to be launched at the end of World War II as part of the Manhattan Project.

As only two atomic bombs were utilized in the conflict, SCP-666-EX initially remained unused, but was deemed a useful asset for early experimentation concerning nuclear weaponry and avoided being harvested for its plutonium. During this era, it remained in the custody of the Los Alamos Laboratory in New Mexico, where two accidents involving it took place during sub-criticality experimentation (See Addendum 666.1). The several deaths which occurred as part of these incidents earned SCP-666-EX the colloquial monicker “demon core”.

Following the accidents, employees of the laboratory began reporting several anomalous occurrences attributed to SCP-666-EX. A report compiling these events was subsequently compiled and distributed to the Foundation2 (See Addendum 666.2). After agents were sent to the Los Alamos Laboratory for investigation, SCP-666-EX was placed into Foundation custody.

Addendum 666.1: Experimentation Overview

It is suspected that the laboratory wanted the Foundation to remain ignorant of the initial experimentation which resulted in the deaths of their personnel. Agents dispatched to the facility were able to uncover the following points of interest regarding the experiments:

  • The goal of the experiments was to determine the limits a nuclear core could be taken to before criticality is reached, primarily undergone by surrounding the cores with objects capable of reflecting neutrons. This is a highly dangerous practice.
  • Little to no safety precautions were taken during the experiments. Nuclear cores such as SCP-666-EX were likely brought to near-criticality on several occasions, almost causing significant damage to the laboratory and casualties if mistakes were made.
  • Small mistakes during the experiments were likely the primary cause of the multiple reported incidents in the facility. The labaratory was lucky to have avoided both sustaining more damage or lost more personnel as part of these incidents.

Due to the nature of these experiments, the dispatched agents considered it unlikely that the United States government would have officially sanctioned their occurence.

Addendum 666.2: Compiled Report

The following is the report provided to the Foundation regarding the anomalous phenomena reported to have occurred due to SCP-666-EX:



Following the events of May 21, 19463, the Los Alamos Laboratory has been subject to large amounts of observed paranormal activity as a result of the continued presence of the object known as the demon core. The following is an assembled list of events reported by laboratory personnel and the dates they occurred.

[5/23/1946]: Personnel observe the lights in all break rooms suddenly begin to flicker uninterrupted for a period of several continuous hours. No direct interference or issues with the lab's electricity could be discerned.

[5/25/1946]: Several members of laboratory personnel claim to hear disembodied voices in the testing room where the May 21st incident took place. One individual claims to have seen an unknown figure out of the corner of their eye.

[5/29/1946]: The demon core is observed to levitate for roughly ten minutes before falling onto the ground.

[6/02/1946]: All three previously recorded events occur during different times of the day, but with a higher intensity. The lights flicker for longer, the disembodied voices are louder, and the demon core levitates for longer.

[6/07/1946]: During the initial arrival of personnel with morning shifts at the laboratory, what appear to be several apparitions are seen in the windows. No exact details of the figures are discernable. All personnel subsequently refuse to enter the lab.

Addendum 666.3: Recovered Communication

As part of the investigation regarding SCP-666-EX, Foundation agents secretly obtained and made copies of all video and audio recordings within the Los Alamos Laboratory during the period in which they were stationed in the area. Viewing of the materials showed significant divergence between the reported events regarding SCP-666-EX and the recordings, with none of the described anomalous events visibly taking place in the footage or audio.

Interest in the investigation eventually shifted towards an audio recording of a secluded back room of the laboratory, the only tape of which had been significantly damaged through what was determined to be purposeful tampering. Personnel eventually managed to isolate and repair a large amount of the audio, revealing it to have been a communication between two unknown parties. A transcript of what could be reconstructed has been provided below:


UNKNOWN [1]: What the hell are we going to tell Washington?

UNKNOWN [2]: Well, whatever we decide on, it can't be what we were doing here. They'd have our heads for this. We've lost too many lives to this shit. If they knew…

UNKNOWN [1]: For Christ's sake. You got any ideas?

UNKNOWN [2]: Well, for one thing, we're gonna need someone to take the damn demon core off our hands and clean this shit up for us.

UNKNOWN [1]: I realize that. Anyone you know who would keep quiet about it?

UNKNOWN [2]: Mm, not sure if anyone I know would keep quiet per say. It's going to get to Washington somehow if we go through anyone in the government. They keep tight records… we all do.

UNKNOWN [1]: Wait a minute, you just made me think of something, there. You know those… agh, what's their name… that Foundation? They're independent of government regulation. Maybe we could go through them?

UNKNOWN [2]: The Foundation? Don't they only take care of paranormal crap? Spooks and phantoms?

UNKNOWN [1]: Well, if they want spooks and phantoms, that's what we'll give them. I can make a few calls today. Think you could draft up a report or something?


Following analysis of this recording, SCP-666-EX was determined to have no anomalous properties and was subsequently reclassified as Explained. Information regarding the true nature of the experiments involving SCP-666-EX and the attempted deception by the laboratory was given to the United States government by Foundation sources.

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