by qntm and CptBellman

Item #: SCP-055
Object Class: Keter
Special Containment Procedures: Object is kept within a five (5) by five (5) by two point five (2.5) meter square room constructed of cement (fifty (50) centimeter thickness), with a Faraday cage surrounding the cement walls. Access is via a heavy containment door measuring two (2) by two point five (2.5) meters constructed on bearings to ensure door closes and locks automatically unless held open deliberately. Security guards are NOT to be posted outside SCP-055's room. It is further advised that all personnel maintaining or studying other SCP objects in the vicinity try to maintain a distance of at least fifty (50) meters from the geometric center of the room, as long as this is reasonably practical.
Description: SCP-055 is a "self-keeping secret" or "anti-meme". Information about SCP-055's physical appearance as well as its nature, behavior, and origins is self-classifying. To clarify:

How Site 19 originally acquired SCP-055 is unknown.

When SCP-055 was obtained, and by whom, is unknown.

SCP-055's physical appearance is unknown. It is not indescribable, or invisible: individuals are perfectly capable of entering SCP-055's container and observing it, taking mental or written notes, making sketches, taking photographs, and even making audio/video recordings. An extensive log of such observations is on file. However, information about SCP-055's physical appearance "leaks" out of a human mind soon after such an observation. Individuals tasked with describing SCP-055 afterwards find their minds wandering and lose interest in the task; individuals tasked with sketching a copy of a photograph of SCP-055 are unable to remember what the photograph looks like, as are researchers overseeing these tests. Security personnel who have observed SCP-055 via closed-circuit television cameras emerge after a full shift exhausted and effectively amnesiac about the events of the previous hours.

Who authorized the construction of SCP-055's containment room, why it was constructed in this way, or what the purpose of the described Containment Procedures may be, are all unknown.

Despite SCP-055's container being easily accessible, all personnel at Site 19 claim no knowledge of SCP-055's existence when challenged.

All of these facts are periodically rediscovered, usually by chance readers of this file, causing a great deal of alarm. This state of concern lasts minutes at most, before the matter is simply forgotten about.
A great deal of scientific data has been recorded from SCP-055, but cannot be studied.
At least one attempt has been made to destroy SCP-055, or possibly move it from containment at Site 19 to another site, meeting failure for reasons unknown.
SCP-055 may present a major physical threat and indeed may have killed many hundreds of personnel, and we would not know it. Certainly it presents a gigantic memetic/mental threat, hence its Keter classification.
Document #055-1: An Analysis of SCP-055
The author puts forward the hypothesis that SCP-055 was never formally acquired by ████████████ ████████ and is in fact an autonomous or remotely-controlled agent, inserted at Site 19 by an unidentified third party for one or all of the following purposes:

to silently observe, or interfere with, activities at Site 19
to silently observe, or interfere with, activities at other SCP locations
to silently observe, or interfere with, activities of humanity worldwide
to silently observe, or interfere with, other SCP objects
to silently observe, or interfere with, ████████████

No action to counter any of these potential threats is suggested, or indeed theoretically possible.
Addendum A:

Hey, if this thing really is an "anti-meme", why doesn't the fact that it's an "anti-meme" get wiped? We must be wrong about that somehow. Wait a minute, what if we were to keep notes about what it isn't? Would we remember those? Bartholomew Hughes, NSA

Document #055-2: Report of Dr. John Marachek
Survey team #19-055-127BXE was successfully able to enter SCP-055's container and ascertain the appearance and, to some degree, the nature of the object. Notes were taken according to the project methodology (see ████████████), after which the container was sealed again.
Excerpt from a transcript of personnel debriefing follows:

Dr. Hughes: Okay, I'm going to need to ask you some questions about number 55 now.
███████: Number what?
Dr. Hughes: SCP object 55. The object you just examined.
███████: Um, I don't know what you're talking about. I don't think we have a 55.
Dr. Hughes: Okay, then, ███████, I'd like you to tell me what you've been doing for the past two hours.
███████: What? I… <subject appears uncomfortable> … I don't know.
Dr. Hughes: Okay, then, do you remember that we all agreed that it wasn't spherical?
███████: That what wasn't… Oh! Right! It isn't round at all! Object 55 isn't round!
Dr. Hughes: So you remember it now?
███████: Well, no. I mean, I don't know what it is, but I know there is one. It's something you can't remember. And it's not a sphere.
Dr. Hughes: Wait a minute. What's not a sphere?
███████: Object 55.
Dr. Hughes: Object what?
███████: Doc, do you remember agreeing that something wasn't shaped like a sphere?
Dr. Hughes: Oh, right!

It appears to be possible to remember what SCP-055 is not (negations of fact), and to repeatedly deduce its existence from these memories.
Personnel involved in Survey #19-055-127BXE reported moderate levels of disorientation and psychological trauma associated with cycles of repeated memory and forgetfulness of SCP-055. However, no long-term behavioral or health problems were observed, and psych assessments of survey personnel showed consistent reports of this distress fading over time.
Recommendations: It may be worthwhile to post at least one staff member capable of remembering the existence of SCP-055 to each critical site.

Next: We Need To Talk About Fifty-Five

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