With all the anomalies the Foundation deals with on the daily, ones that can cause the apocalypse are quite prominent.
- A distressingly large number of SCP objects can cause (or have caused) The End of the World as We Know It, to the point where the Foundation is actively predicting and categorizing the different ways the world can end, using the (fictional) "K-Class" classification system. note
- AK-Class Madness scenario: When humanity suffers a mental block on normal activity on a scale massive enough to totally disrupt the lives of those affected. In other words, something makes the world irrevocably go mad. SCP-1101
has the potential to create such a runaway scenario if a containment breach allows a chain-reaction of people to become exposed to the anomaly, join the debate, and begin to draw other people into the anomaly. SCP-571 and the viral memetic property that gives affected people a compulsive need to spread the meme also carries the risk of causing such an event. - AE-Class Total Allison Eckhart Failure Scenarionote : The Earth is fully contaminated in gaseous anomalous (or non-anomalous) substances. Used once in SCP-2565/Allison Eckhart, where a Group of Interest obtains the waste samples of the titular semantic pointer and uses them to infect the world, causing every physical object on Earth to be defined, perceived, and only able to be referred to as Allison Eckhart.
- CK-Class Restructuring scenario: It doesn't end the world outright, but the world is so different that it might as well be gone. One example of a CK is SCP-140. The longer the book grows, the longer the gruesome Daevite civilization in the book survives in real life. Making it long enough would change modern society beyond recognition. Another example is the Wrong Proposal, which outright states at the beginning that our history is the result of a CK-Class. It was initiated primarily because many pre-1900 events equivalent to the ones we know today were loaded with anomalies, leading to Earth becoming a bit of a Crapsack World.
- EK-Class Evolutionary Restructuring Scenario: Life on Earth is forcibly evolved into unrecognizable conditions using artificial instigation of the rubber-band nature of evolution. Used in SCP-3069, where an anomalous underwater structure 20 Minutes into the Future threatens to poison the Earth's oceans and accelerate the evolution of life to recreate all aquatic fauna in its image.
- EK-class Loss of Consciousness scenario: When humanity as a whole suffers a loss of self-awareness, that may not kill people but does remove their free will in some form. Can create a scenario where all humanity loses the ability to resist suggestions by whatever authority controls the object.
- GK-Class Hostile Greenhouse scenario: When plant life would severely disrupt the planet. Used in SCP-540 where anomalous weapons cause plants to bloom. It contains a modified Tsar Bomba, a 75 megaton nuclear weapon that would cause a forest to break out over one third of the planet.
- GH-0 Dead Greenhouse: Described as what happened in the document recovered from the Marianas Trench as a result of multiple SCP's breaching containment. Everybody on Earth dies, but the planet is still capable of supporting life.
- IK-class Global Civilisation Collapse scenario. One story has a (perfectly normal, non-anomalous) asteroid that would kill 3 billion people over the next 10 years when it hit Earth being called an IK-Class natural disaster. This could also happen if there's an overpopulation of rock-eating fish that will eventually collapse the Western coast of the United States, not only killing millions of people but inflicting massive damage on the environment, technological infrastructure, and global economy, as well as displacing millions of survivors as refugees and causing a major political crisis. And by "if" we mean "it's happening in about 30 or so years".
- MK-class Total Loss of Human Consciousness scenario: All of humanity loses most of their higher-order thinking. The nature of the scenario is used multiple times but was not given a name until SCP-3002 was created, where a sapient idea destroys most of the Foundation, infects nearly all of humanity and all information in the world, and forces the Overseer Council to kill 11 of their members. Because ideas are bulletproof, the story ends on a cliffhanger with two possible outcomes: either Veles, O5-1, resets the world, or the idea hijacks all of the population and cuts off their free will. The latter is more likely to some extent. Also, it should be noted the ending doesn't say if the O-5 council was eliminating infected members... Or, the other way around. Also, SCP-3733 is implied to take place in a post-MK world.
- NK-Class Replication scenario: An object that is self-replicating or able to create matter out of nothing spirals out of control, and Earth becomes uninhabitable because it's completely covered in ink or cakes or coffee or what have you. Though harmless to our world, SCP-1689 is heavily implied to be a portal into a world where this happened with potatoes.
- PK-Class Existential Pandemonium Scenario: A proposed class, in which a higher entity does not have the intelligence needednote to process higher metanarrative threads of information (essentially, universes higher up on the metanarrative order that can contain lower ones in the form of fiction), and as a result, suffers sensory/cognitive overload. As a result, all lower narratives are compressed into one, wreaking havoc on our reality as each reality overlaps with each other in an unrecognizable mess. This was proposed in relation to the dangerous reality-warper SCP-3812, but ultimately rejected for being deemed implausible. In fact, the process was well on its course.
- QK-Class Quantum Degeneracy scenario: When earth disintegrates into a quantum mess. SCP-2460, a piece of anomalous dark matter, can convert normal matter into more dark matter like itself, causing them to maintain their shape but lose the repulsion between particles, effectively causing objects to “phase through” each other. Should the object collide with earth, it will turn the entire earth into a giant bulk of orbiting non-interacting matter.
- SK-Class Dominance Shift scenario: The dominant species being made extinct or forced into subjugation by another species. This could happen if a currently contained species became aware of, then began direct competition with humanity; when a replicating human is unable to be contained and it takes over the planet, or when humanity rose up against a dominant sapient species during our pre-history and took control over the planet..
- TK-Class Causal Restructuring Event: The world or part of it is changed to a state similar to an earlier era. Described in the article for SCP-1297, a jar of human toenail clippings that rolls history back by up to a century per nail clipping removed from it. An addendum to the article implies this has already happened — there is one clipping missing.
- UK-Class Global Irradiation Event: The world becomes polluted with radioactivity. Mentioned in SCP-2493, where the potential cause is the body of an extradimensional person made of antimatter colliding with Earth's atmosphere.
- XK-Class End of the World scenario: Was originally used in relation to religious-based ends of the world, but shifted to an "all-purpose" of the end of the world scenario that could be anything from "humans died" right up to "the death of all life on the planet" or even "the entire planet is exploded". It's bad news, whatever the end result is. Dr. Clef's proposed SCP-001 if moved in confluence with a breach in SCP-995note and the opening of SCP-616 is just one example.
- YK-Class Entropic Annihilation Event: Causing the entire universe to reverse its flow of entropy, effectively turning time backwards. SCP-2700, Tesla’s Death Ray, contains a bundle of anomalously contained particles that behave against normal entropy as its core. Should the death ray fire, the particles would be released and the entire universe will be converted to reverse entropy. A YK event happens every two weeks inside SCP-2123.
- ZK-Class Reality Failure Event: Reality as we know it is destroyed, and may or may not apply to multiple other realities. One of SCP-001's proposals mentions a non-zero possibility of a total metaphysical annihilation of the universe. Because they are the authors of the universe.
- ZK-0 Reality Failure: Similar to above, but the universe would still exist, just not under our laws. The universe on the other side of SCP-319 is in a lower energy state, so should the device fail to contain the universe portal, a vacuum metastability event would occur, bringing the entire universe into a lower energy state that can’t support anything our current universe has.
- AK-Class Madness scenario: When humanity suffers a mental block on normal activity on a scale massive enough to totally disrupt the lives of those affected. In other words, something makes the world irrevocably go mad. SCP-1101
- Some SCPs and tales indicate the world has already ended several times. In some cases the Foundation survivors used some version of time travel or retconning to prevent the events that led to the disaster. More disturbing are incidents where the Foundation, seemingly utilizing SCP-2000, simply cleaned up the surface and repopulated the world with clones, rewriting history to account for any inaccuracies, with the implication that nobody knows how many times they've done this.note And the cloning system that allows it is in bad shape.
- A few alternate dimensions have suffered this fate, usually due to an improperly contained SCP. The Foundation also accidentally caused this in at least one reality by giving them a vaccine which turned out to be a Sterility Plague. SCP-2935 is a case where all life on the planet is wiped out without doing outright damage to the planet itself.
- In 2018 the site ran the Doomsday Contest, in which each team had to come up with four documents centred around a unique __-Class Scenario of their own invention. There are 44 teams, so that's potentially 44 new world-ending scenarios from a single contest. They include:
- TPK-Class Thaumaturgic Proliferation Scenario: All of humanity gets infected by SCP-3396, an alien symbiote in the form of a blue liquid, and transforms into SCP-3731, changing their appearances and gaining various powers in the process. Once there are no more normal human beings left, all SCP-3731 entities will leave Earth and Ascend to a Higher Plane of Existence.
- ΩK "End of Death" Scenario: Death no longer happens to any and all living beings and they all become The Ageless and gain Resurrective Immortality, complete with drawbacks such as Age Without Youth, Came Back Wrong, and feelings of Who Wants to Live Forever?. Society is irreversibly changed but adapts accordingly and tries to find workarounds to the drawbacks mentioned.
- ED-K-Class Lethe Scenario: All of humanity is infected by SCP-3848, a Mind Virus that gives you Laser-Guided Amnesia and can give you not only the Loss of Identity, but can erase the concepts that make up normal human morality, having some of the infected exhibit Blue-and-Orange Morality. The Foundation discovers a treatment by neurally implanting artificial memories, but eventually finds humanity to be a lost cause and leaves Earth to find other worlds to colonize.
- End-of-World K/O Failure Scenario: In the Shark Punching Center timeline, the sharks have overwhelmed the organization to the point where they simply are unable to punch all of them. Their solution to the problem led to a variation of this scenario in the main Foundation timeline where all human beings become infected with SCP-3760 and slowly turn into sharks.
- MA-Class Mass Animation Scenario: Enough Animate Inanimate Objects have formed to the point where the Foundation cannot contain all of them and maintain the pretense of normalcy. Humanity now has to live with the objects they've formerly used but are now given life.
- ☿K-Class "World of Babel" Global-Incomprehension Scenario: All of humanity is infected by SCP-3432 after it advances from its original form to a Mind Virus that causes progressive, total, and irreversible loss of the ability to communicate. Everyone ends up locked in their own heads, still able to think but unable to put together or understand any form of communication; anything that can transmit concrete information (spoken, written, or signed language, interpretive dancing, pictograms, etc.) is now impossible.
- SCP-3799 is a type of snow that expands by dissolving human corpses. Kinda creepy. Then it turns out that it has a memetic effect that makes people view the snow in religious awe and willingly go to die of hypothermia to become fuel. It eventually consumes more than 40% of the planet. And even worse, the memetic effect becomes worse over time, either affecting human memory and records, or outright rewriting history in its quest to make everything pure and uniform. By the end, the Foundation has been rewritten into the SCF, Snow Containment Foundation, whose main goal is to contain the snow. And they fail. Ultimately, only a few humans remain, completely convinced that the world has always been covered in snow, and that humans have always lived inside the Foundation sites. The snow is finally stopped by someone performing a Heroic Sacrifice, after somehow overcoming the memetic effect.
- SCP-4005 is an odd example in that while the world as we know it completely ends, humanity as we know it doesn't. They are all simply offered something better, along with a pilgrimage to follow to get there. One by one, they get the visions of where, what, and how. And one by one, they just leave. And in the end, the Earth is completely empty, because every last human just up and walked away into what is implied to be a genuine, extradimensional Utopia. It'd be played straighter if it was a trap all along, but we never get any such hints.
- Revised Entry has SCP-173 gain the ability to self-replicate, doubling to the point where instances become impossible to contain. They escape, begin massacring the populations of North and South America. Groups of thousands are powerful enough to destroy Foundation facilities and they even manage to rip SCP-682 to pieces. The O5's declare it an XK-Class, pull the few surviving Foundation staff out, then conduct a saturation nuclear bombing campaign. The Americas are declared Containment Zone X1, and all remaining Foundation resources and the entire remaining world's navies are to constantly patrol the coasts and scan the oceans, making sure nothing escapes. The final addendum confirms SCP-173 has been spotted in Wales...
- SCP-5000 invokes this scenario, mostly consisted of archives and data from a high tech suit that functions as a Perception Filter. Its deceased occupant is a survivor from an alternate universe, and filled the suit's databanks with an Apocalyptic Log detailing how the SCP Foundation suddenly reversed their creed of "We die in the dark so that others can live in the light" and launched a campaign to exterminate the human race. The main motivation of carrying out an all-out war against humanity isn't clearly stated, naturally, as noted by the SCP-5000 user being annoyed at the pretentious usage of redactions in their protocols and instructions used to carry out the assault. The user details how dozens of SCPs such as SCP-096 and SCP-1048 are being weaponized against humanity and various GOIs like the Church of Broken God and Global Occult Coalition, while any SCPs that were fundamentally human or had human sympathies were destroyed. By the end of the logs, the whole world is now inherited by the newly-freed SCPs, and the Foundation's forces have been replaced by mutated troops given the attributes of SCP-173. If one does some digging through this article, the Foundation's reason for killing the human race appears to be the discovery of an Eldritch Abomination inhabiting the collective human psyche, which is responsible for humanity's ability to feel pain. While the entity's motives are unknown, the Foundation immediately decided that the entity had to be stopped, and that exterminating mankind was somehow the most ethical solution — the groundwork for this was set by memetically altering their staff to no longer feel pain, or empathy for the pain of others. Thankfully (or unfortunately, depending on what exactly the entity has in store for us), SCP-5000's user, one of the last uncorrupted Foundation personnel, managed to create a Reality-Breaking Paradox that restored the world to an earlier point. But since that universe was reset to just before the discovery of the entity, there's no way to tell whether or not it will happen again.
- SCP-6000 "The Serpent, the Moose and the Wanderer's Library" is a more positive take on the end of the world. The version of the world that the story is set in has naturally reached its end, and the entire world is consumed by the Wanderer's Library. The stories of the world are turned into books and added to the shelves, and the earth itself becomes another wing of the Library. The people don't die, either. At the end of the article, they are all sitting peacefully and reading, patrons of the Library.
- SCP-6187 ('From Space With Love') is a species of Space Whale, which migrate from star to star, eating smaller spaceborne organisms. They communicate through radio signals, and unfortunately, one has latched onto Earth's broadcasts, and mistaken our planet for a member of its own species - in short, Earth is in danger of literally getting fucked to death.
