Per 
Looking for a greenlight: "The Murdered World / Anglerfish Singularity"
Preliminary summary: (you can skip this)
While testing the settings of dimensional gates, the Foundation finds a reality with a black hole where another Earth should be.
Enemy action?
Common sense should dictate that the Foundation stays the hell away from this place, but there are complications.
Specifically, having access to a space vacuum and a planet-scale black hole next door is very, very useful for space travel (for reasons I go into at length in the sandbox) and the Foundation is not immune from pressure by goverrnments and commercial groups.
-The horror element is not the black hole itself, but the knowledge that *someone* crushed a living world and its inhabitants into a singularity.
That someone has now departed, but could very well have left automated sentinels behind.
Yet -unbelievably- there are people who would risk alerting those destroyers to our existence in pursuit of temporary convenience and profit.
NB -there are *many* stories about dead worlds.
And there are *many* stories about artefacts acting as bait, from Arthur C. Clarke's 1951 "Sentinel" to SCP-2100.
But this is different, because the singularity is *both* a mass grave/murder scene, and a bait, luring in the unwary.
You might say "no one would be stupid enough to risk attracting the attention of genocidal entities who crushed a planet into a singularity".
But current events show humankind has an infinite capacity for self-delusion.
Can the O5 council prevail, if a coalition of interest groups led by Marshall, Carter & Dark really pushed?
-To add to the horror, the moon orbiting the absent Earth has a lunar habitat with the bodies of astronauts who survived for two weeks before the air ran out. The records they left behind document the despair of the doomed group, literally the last men alive.
Earth analogs in adjacent phase space have been colonised by aliens before intelligent life arose locally, and very few terrestrial organisms remain giving an ominous glimpse of the ambitions of this rival species.
Attribution: The inspiration for this idea came from a plot element in a novel by Charles Stross. The author has given me permission to develop the idea in the context of SCP wiki horror/SF.
- - - - - - - - - - - -
Item #: SCP-XXXX
Object Class: Safe
Special Containment Procedures: SCP-XXXX is not currently present. SCP-XXXX-1 is self-containing as it can only be reached through the dimensional gates SCP-[redacted] and SCP-[redacted]. These SCPs already have containment procedures in place.
Description: The device/process initiating the cataclysmic event that caused the destruction of a planet, the death of its inhabitants and the creation of a black hole (SCP-XXXX-1) is designated SCP-XXXX.
SCP-XXXX-1 is a singularity / former planet with a mass exactly the same as Earth discovered in an adjacent reality.
The black hole is orbited by a moon identical to Earth's moon and by orbital debris composed by iron, copper, silica and aluminum, the elements used to build satellites.
Discovery: Testing of the settings of dimensional gates SCP- [redacted] opened up a way to a vacuum. After installing airlocks, automated probes connnected with cables to the gates found themselves suspended over an airless abyss surrounded by stars in all directions. The constellations were identical to those visible from Earth. A moon with a diameter and orbital period identical to our moon was orbiting a point 6400 km below the probes.
High-energy (x-and gamma-ray) detectors confirmed that the point one Earth radius below the gate contains a black hole, emtting Hawking radiation and having a very tenous accretion disc containing interplanetray dust. There is no satisfactory cosmological theory accounting for a natural event creating a planet-sized black hole.
Any satellites in low orbit around the former world would have been vaporised by the energy released dring the cataclysmic event. A systematic search using microsatellites revealed many lumps of metal and silica in geostationary orbit with a mass and composition consistent with satellites that have melted and then solidified.
Exomoon:
As the heat loading at lunar orbit would be only one per cent of that in geostationary orbit, probes have been sent to the moon aka SCP-XXXX-2 to search for more intact artefacts.
The partially molten remains of nine Apollo lunar landing stages were eventually discovered on the lunar surface. The remains of several L3M crewed Soviet lunar vehicles were also found. Plaques celebrating lunar landings signed by L. Johnson and N. S. Khrushchev were recovered.
Probes found a a weak radio beacon at Mare Marginis on the moon of SCP-XXXX-1.
Robotic exploration revealed the remains of a lunar habitat. The aboveground facility was destroyed, but a shaft leading into a lava tube cave revealed intact crew quarters and storage facilities. Six human bodies were found in the sublevel. Name tags identified them as G. Grissom, V. Komarov, A. Leonov, W. Schirra, C. Sagan and J. C. Fletcher.
As the sublevel had been shielded from radiation, heat and EMP, equipment was intact and the six persons had survived for two weeks before running out of power for the air CO2 scrubbers.
They had used the time to write down an account of events, assemble mineral samples and other items of scientific interest, and putting together a radio beacon powered by an isotope battery.
Documents referred to a magnetic anomaly in Tycho crater being investigated just prior to the cataclysmic event.
Near the bodies was a table arranged like an altar, where they had assembled items of apparent personal importance. These include a photo showing Grissom, Stewie Wonder, Marilyn Monroe, Walter Mondale and two persons who appear to be Secret Service agents. The photo is signed "to Gus from W. Mondale, 1972".
There is a record, labelled "The Silver Beatles Live at Hammersmith Odeon 1975". This has the name "Carl" written on the sleeve.
There is also a videotape made by the six persons after they were trapped on the base. Personnel that have watched the tape have required counselling afterwards. The contents of the tape has been restricted to Foundation members of level 4 or above.
Hypothesis :
The civilisation of the dead former planet may have encountered and activated a "sentinel" left by a hostile spacefaring civilization who does not want competition from emerging rivals (see concept by A. C. Clarke, 1951) ultimately leading to extermination by an unknown process turning the whole Earth into a black hole.
Utility:
Despite the morbid background, there is considerable interest in using SCP-XXXX-1 to facilitate spaceflight, as it combines gates to vacuum and a singularity that can be used for powerful gravity assists, making spaceflight cheaper and easier by several orders of magnitude.
The cheaper launches are expected to increase the market for satellites by 80 billion USD, a fact that many governments keep raising with the Foundation. The Foundation still has a monopoly on dimensional gates, but Marshall, Carter & Dark has hinted it has access to portals that can be bought by those able and willing to provide enough power and money. The prospect of opening a gate without Foundation control is codenamed "Case Moria Balrog"
Potential danger: Dr. Tarantoga is strongly opposed to *any* use of SCP-XXXX-1, as the planet-destroying entities already have demonstrated genocidal intent, and may have left AI sentinels in the planetary system of SCP-XXXX-1. Such sentinels need only become active once in a century, so they cannot be traced by their energy signatures.
Civilizations who practise dimensional travel along with spaceflight will sooner and later find SCP-XXXX-1 and be tempted to use it. Dr. Tarantoga regards SCP-XXXX-1 not only as the remnant of a genocidal war, but bait, deliberately left behind to lure emerging technological species to reveal themselves. Dr. Tarantoga argues that if only a single genocide had been the goal of the planet destroyers, they could have achieved this by ordinary nuclear, chemical and biological weapons using much less energy.
Addendum: After exploring other settings on the dimensional gates SCP [redacted] in nearby phase space, the researchers found a planet seemingly inhabited. Stealthed probes operating in unpopulated areas found that only bacterial life shared terrestrial DNA with our world, all larger organisms have a quite different set of DNA consistent with colonisation by an extra-terrestrial civilisation. Continued exploration of this world was terminated for security reasons.
Two other nearby gate settings gave the same result, with similar extra-terrestrial DNA present on the local Earth analog.
Conclusion: This section of the dimensional phase space has been colonised by an aggressive extraterrestrial civilisation that has no use for neighbors or potential rivals.
Addendum: Dr. Tarantoga has attempted to get SCP-XXXX-1 classed as a cognitohazard, as by its nature it tempts any technological civilization to use it for cheaper spaceflight, thus attracting the attention of the hostile entities/hostile civilization that destroyed the planet.
This suggestion has been rejected as it does not formally fit the definition of a cognitohazard.
Addendum: Dr. Tarantoga has attempted to get any use of SCP-XXXX-1 classed as a potential xk-class scenario, as this may attract malign aliens with planet-destroying abilities. Decision is pending by the O5 council.
Approval is expected to lead to an open conflict with Marshall, Carter and Dark, not to mention the national governments and corporate entities with strong commercial interests. A political and military conflict with such a coalition will not necessarily lead to an outcome that favors the Foundation.
