A-YK Class senarios

* **AK-class end-of-the-world scenario**
	+ **Definition:** End of the world via restructuring of subjective reality - that is, the perceptions and/or thought processes of the human race. Simply put: "everyone goes crazy", by one fashion or another.
	+ **Moose's Notes:** Multiple references using similar definitions have appeared independently of each other in various works. This can also be thought of as a "restructuring" scenario; but it would typically be termed as an "end of the world" scenario because effectively, for humans, the world *has* ended, just as thoroughly as if civilization got all blowed up.
	+ **Appearances:**
		1. Change
			- Scenario is first referenced and established as a scenario involving reality shifts, related to BK-class undefined and CK-class restructuring.
		2. SCP-571
			- Scenario is a the permanent alteration of behavior in all or the vast majority of the human race, caused by a memetic pattern with a piggybacking anomalous effect that forces the user to permanently fixate on spreading it.
		3. SCP-1101
			- Scenario is a perpetual argument encompassing all or the vast majority of the human race, caused by a mind-altering device with an exponential effect.
* **CK-class restructuring scenario**
	+ **Definition:** Restructuring of reality. May mean a significant change in history (rewriting the present to match), or a change in the way physical laws work, or in the way the universe works, or a major rewriting of reality encompassing some or all of these.
	+ **Moose's Notes:** The original restructuring scenario. May have been created by an ex-site member (and called "CK-class reconfiguration") but as their work no longer exists, their usage of it is irrelevant. The only-used-one "CK-class end of the world scenario" may be a subset of this scenario (see below).
	+ **Appearances:**
		1. SCP-140
			- Scenario is retroactive restructuring of modern society based on alterations to timeline.
		2. Of Multiverses and Dandelion Wine
			- Scenario in which the multiverse is collapsing, universes merging together.
		3. Incident 239-B - Clef-Kondraki (SCP-239)
			- Scenario is a reality bender rewriting reality as we know it.
		4. SCP-1237
			- A wide variety of wide-scale non-apocalyptic reality shifts.
		5. Change
			- Scenario referenced along with AK-class and BK-class scenarios as one of three scenarios involving reality shifts.
		6. Recovered Data File
			- Scenario involves multiple CK-class events, some deliberately initialized by the Foundation, apparently attempting to repair or control an ongoing restructuring scenario.
* **GH-class "dead greenhouse" scenario**
	+ **Definition:** Life as we know it is 80% or more dead, but the planet can still be fixed, more or less, and can still support life.
	+ **Moose's Notes:** Also referred to a "DG-class scenario" unofficially (by author Dr. Gears in discussion).
	+ **Appearances:**
		1. Document Recovered From The Marianas Trench
			- Scenario is near-total SCP containment breach, causing widespread destruction and chaos in which most of humanity dies, and the Foundation must rebuild the world to an approximation of what it once was. Referred to as "GH-0".
* **NK-class end-of-the-world scenario**
	+ **Definition:** End of the world caused by self-replicating material.
	+ **Moose's Notes:** Also referred to as the "grey goo" scenario. Once defined as a scenario characterized by an explosive event with effects on a geological scale; this definition can be considered defunct, as the current definition has been widely accepted (and the earlier definition seems excessively specific).
	+ **Appearances:**
		1. SCP-505
			- Scenario is massive-scale environmental contamination caused by self-replicating ink.
* **RK-class restructuring scenario**
	+ **Definition:** Out-competition of standard Earth species by non-standard life-forms.
	+ **Moose's Notes:** Definition taken from SCP-816 and thus may be excessively/inaccurately specific. Alternate suggested definition: World is changed, but humanity, history, and rules of reality are the same.
	+ **Appearances:**
		1. SCP-816
* **SK-class dominance shift scenario**
	+ **Definition:** Changing of the planet's dominant species.
	+ **Moose's Notes:** In the modern day, indicates a shift to dominance by another life form, or humans of alternate form and/or culture.
	+ **Appearances:**
		1. SCP-752
			- Scenario is competition between modern-day humans and genetically/socially re-engineered humans, projected to result in dominance shift.
		2. SCP-1000
			- Scenario is shift in which humanity becomes the dominant species of Earth by driving another species to near-extinction and destroying their civilization semi-permanently.
* **XK-class end-of-the-world scenario**
	+ **Definition:** "Salted earth" end of the world scenario; in other words, destruction of the world as we know it with little possibility of immediate rebuilding. May include (but is not defined by) threat of species extinction.
	+ **Moose's Notes:** The original end-of-the-world scenario. Formerly meant a religious apocalypse in line with some variant of Abrahamic religious beliefs (usually as a direct result of a major religious event or artifact); expanded further to the above definition. This term is also used as a shorthand or slang term for all apocalyptic scenarios.
	+ **Appearances:**
		1. Dr. Clef's Proposal for SCP-001
			- Scenario is a Biblical apocalypse of some variant.
		2. SCP-152
			- Includes many XK-class scenarios that involve the extinction of humanity. Specifies that apocalyptic events that involve the extinction of humanity are **not** all classified as XK-class scenarios.
		3. Revised Entry to SCP-173
			- Scenario involves alternate-universe version of SCP-173 gaining the ability to multiply with a hive mind, wiping out most of the human population of North America, South America, and the United Kingdom, followed by saturation nuclear bombing.
		4. SCP-227
			- Two example XK-class scenarios are given: wandering brown dwarf (the so-called “Nemesis hypothesis”) or a gamma ray burst. Other apocalyptic cosmic events that are classified as XK-class scenarios are implied.
		5. SCP-231
			- Scenario involves a Satanic cult-induced pregnancy (serving as a "seventh seal") being ended or carried to term, resulting in a supernatural/religious apocalypse.
		6. SCP-435
			- Scenario involves SCP-435-2, the 'shadow' of an extra-dimensional entity, causing massive widespread destruction on a nuclear detonation scale at minimum… to start. Prevented only by keeping SCP-435-1 under bright light. A last-resort preventative is Contingency 435-XK-Alpha.
		7. SCP-616
			- (Fictional) procedure involves destruction of (supposedly) Abrahamic-religion-based SCP in event of any XK-Class end-of-the-world scenario.
		8. SCP-701
			- Specifically *not* an XK-Class scenario (only kills hundreds of people a year).
		9. SCP-861
			- Variety of scenarios based on Judeo-Christian religious beliefs. Refers to XK-400 and XK-423 through XK-436. XK-400a involves YHVH; XK-440c through XK-440v involve either the Seven Seals or entities associated with the Seven Seals; SCP-861 is preliminarily designated XK-440x; XK-423 involves Leviathan.
		10. SCP-923
			- Scenario involves permanent alteration of landscape to create insanity in addition to severe spatial and temporal disturbances and various other worse (classified) effects, including materialization of something classified.
		11. SCP-1023
			- Scenario involves the detonation of a record number of nuclear detonations within a short period of time.
		12. SCP-1200
			- References an apocalyptic scenario that can be prevented by "containing and manipulating the cognitive patterns of SCP-███-█", a human child (possibly SCP-231-7).
		13. SCP-1237
			- Used to refer to a variety of possible apocalyptic scenarios caused by rewriting parts of reality via dreams (as distinct from the CK-class scenarios considered more likely to result).
		14. SCP-1591
			- Scenario involves a device that could theoretically dissolve the entire Earth, and certainly the organisms on it.
		15. Stratagem (SCP-008)
			- Release of SCP-008 (zombie virus) said to likely result in an XK-class or XC-class scenario.
		16. To Sleep, Perchance to Dream
			- Scenario involves using Protocol XK-0272/A as a reaction to a mass (potentially species-wide) deadly infection; protocol requires destruction of all major worldwide population centers.
	+ *Shorthand & Slang References: (May not actually be technically classified as XK events/scenarios)*
		1. SCP-096
			- Scenario involves near-unkillable creature breaching containment and killing the majority of the human species; likely slang.
		2. SCP-108
			- Used to refer to all apocalyptic scenarios.
		3. SCP-523
			- Used to refer to all apocalyptic scenarios.
		4. SCP-630
			- Contamination of water supply which would turn warm-blooded life into black non-reflective blind heat-seeking zombies is referred to in a researcher note as a "kind" of "XK event"; likely slang.
* **ZK-class reality failure scenario**
	+ **Definition:** Reality failure; may or may not be only one of many realities. May include end of all reality.
	+ **Moose's Notes:** Proposed multiple times before finally being used, always in the same sense.
	+ **Appearances:**
		1. S. Andrew Swann's Proposal for SCP-001
			- Scenario is the possible failure of the Foundation's reality.

**B-Level Scenarios**

(Used in a less well-known SCP article or Foundation tale, or is vaguely defined but used in multiple pieces.)

* **BI-class biological invasion scenario**
	+ **Definition:** Invasion of Earth by extraterrestrial life-forms.
	+ **Moose's Notes:** Implies some kind of distinction between extraterrestrial biological and non-biological invasion. Not widely accepted, but potentially usable.
	+ **Appearances:**
		1. The Bacterium, Part One, Part Two, Finale
* **CK-class end-of-the-world scenario**
	+ **Definition:** End of the world via wide-scale (or total) restructuring of the physical mass of the world.
	+ **Moose's Notes:** Seems to be a specific subset of the CK-class restructuring scenarios.
	+ **Appearances:**
		1. SCP-1053
		2. SCP-1012
* **EK-class undefined scenario**
	+ **Moose's Notes:** Does not end human life. Possibly destroys society. Possibly destroys most or all of human consciousness.
	+ **Appearances:**
		1. SCP-338
			- “a looped recording of survival instructions, rendezvous locations, and status updates about "The Great War", and seems to describe an EK-class scenario caused by the release of SCP-███. The contents are changed and updated sporadically, ranging from twice daily to once every 3 weeks.”
		2. SCP-1427
			- Involves extinguishment of all human consciousness within approximately 215 days.
* **IK-class collapse-of-global-civilization scenario**
	+ **Definition:** Collapse of global civilization of a fashion that does not fall under another scenario.
	+ **Moose's Notes:** Scenario did not originally imply any SCP containment breach, just any truly massive natural disaster. Later expanded to be defined as global civilization collapse (often caused by natural disasters on a massive scale).
	+ **Appearances:**
		1. SCP-1238
			- Scenario is a partial collapse of continental plates that would destroy major population centers.
		2. In the Big League
			- Scenario is an asteroid strike with estimated casualties of approximately three billion over ten years.

**C-Level Scenarios**

(Used in an SCP article or Foundation tale, but undefined.)

* **BK-class undefined scenario**
	+ **Moose's Notes:** Explicitly related to AK-class undefined and CK-class restructuring. This, like the others, is a scenario involving reality shifts. Likely a restructuring scenario.
	+ **Appearances:**
		1. Change
* **XC-class undefined scenario**
	+ **Moose's Notes:** Probably a redundant class at this point; used as a throwaway and not necessarily very usable. Alternatively, a C-class scenario could reflect a 'partial' K-class scenario; for instance, an XC-class scenario could be the destruction of a specific sub-section of humanity, say, with genes that made them susceptible to a certain anomalous thing (while the rest of humanity survives).
	+ **Appearances:**
		1. Stratagem (SCP-008)
			- Results from an SCP-008 outbreak; XK-class scenario suggested as similar likely alternate result.

**D-Level Scenarios**

(Unused, but proposed or referenced *multiple* times in discussion. These definitions have a tendency to change.)

* **YK-class vacuum decay scenario**
	+ **Definition:** Vacuum metastability event, wiping out all life and reality.
	+ **Moose's Notes:** Proposed by "The\_Raven", used only in a deleted article. Seems a bit overly specific.