Mnemosyne

The Overseer preparing to administer Mnemosyne

Mnemosyne is the drug used to force memory loss and/or suppression in subjects gathered in the facility. It's creation, research, and study is spearheaded by The Overseer, who runs both the aboveground facility, and the underground operation. The drug is shrouded in mystery for a majority of the series, and the only thing that is initially known about it is its general effect on subjects.

Most all understanding of the drug, how it works, and how it affects others is gathered by Ten through personal experience, close observation of its effects in the other Numbers, discussions about previous subjects, inference, or doctors' explicit statements on the drug.

## Properties

The drug is colorless and clear, no notable tint to it the way other drugs have had. It's not said whether it has a particular odor, but Ten has seen vials of the drug in Chapter 67. It appears most doses vary in number, but are always labelled as NMSNE-###. What the number means is unknown, though it's possible all drugs made at the facility follow this acronym-number format, as Red Valentine apparently does too.

## Procedure

Doses of Mnemosyne are given to subjects via cranial injection, through the back of the neck. A fine needle is pushed into unconscious subjects so that the drug can be administered in any particular spot (the precise spot is unknown at the moment, though there are many areas of the brain associated with memory). The exact procedure is still unknown, but most of what we learned of it was gathered during Chapter 67.

### Location

Not much is known of the room seen in Chapter 67. It is mainly shrouded in shadow, aside from a large lamp above the area where the procedure takes place. There are wires stemming from the area that likely lead outward toward plugs, and against one of the walls is an X-ray light box that displays radiograph images of different parts of patients' bodies. To the sides of the main area and in front of subjects are screens that likely display vital information during the procedure. Little else is known of the room otherwise.
### Positioning

Subjects first appear to be placed in a chair and seated in something akin to Fowler's Position, with a head support placed on their forehead to keep the subject's neck exposed and open as they remain with heads tilted forward and downward.
Ten was never explicitly put in Fowler's position, but the chair she was in had features which made this method apparent. She herself remained strapped into the chair, likely meaning that other subjects are also strapped in this way in the unfortunate case that they wake up during a procedure, something The Overseer has explicitly said happens on occasion in the same chapter.
Subjects also appear to be gagged just in the case that they awake before or during a procedure and start to scream, something The Overseer has also said is fairly common. Gags are more than likely removed if administration of anesthetic or oxygen is necessary.
### Preparation

Subjects are next prepped by having a portion of their hair cut off or trimmed at the back of the neck where the cranium and neck meet, and the area of skin where the needle will pierce is sterilized. Subjects by this point have already been anesthetized, likely by some other anesthetic than the one used more copiously in the story given that Ten was seen being given an oxygen mask.
### Process & Afterward

It is unknown just how long the process of injection takes, or how long the drug takes to start affecting an individual's memory centers, neurons, synapses, etc. Much of the process following a primary injection is also not entirely clear, though it was learned in several chapters during Ten's confinement in The Overseer's room that a series of interviews usually happens after patients have recovered from their first dose, usually involving direct lines of questioning or tricky methods to gauge what and how much the subject affected knows of their life. More than likely, this is done to gauge how effective the drug was at subduing or eliminating memory and memory connections.
Oddly, in video feeds witnessed by Ten of her friends' interviews, some of them seemed to be aware of specific facts about their lives, even if they weren't totally sure about anything else. What happens after a subject proves initial failings in their dose of Mnemosyne is unknown, but evidently The Overseer does not immediately discard patients after this. Given that the Numbers currently have no idea about the things they once said they knew in those feeds, it's possible The Overseer administers another dose of Mnemosyne, or does some other related procedure to facilitate the effects he wants.
## Key Effects

As Mnemosyne is still shrouded in mystery, the intended effects are not quite outlined. Only the desire to stifle memory, completely block it, or sever memory connections are things that have been said or gathered so far in the story. For all patients, memories are completely blocked off or eliminated, and they cannot remember anything about their past.

Because Mnemosyne is evidently still being tested, all its versions may have different effects, or may have different levels of effectiveness. Some patients are said to have recovered bits of memory, and in Chapter 81, it's been made clear that some subjects may occasionally have specific fragments of their memory come back to them. Often, they may not realize these fragments are significant, such as Ten who, in the same chapter, seems to struggle with a memory that constantly leaves her, or else does not make an impression she can connect with. In the case of The Garden, she knows now it's familiar to her, yet still cannot remember it. As learned in earlier chapters of Ten's confinement, sometimes pieces of information can be explicitly given to patients in an attempt to evoke a reaction from them, likely as a means to test the drug's effectiveness. This appeared to be the case with Cyrus, who at one point was given his real name to no significant effect.

## Side Effects

The main effect of memory loss in patients dosed with Mnemosyne are usually stable, but each subject will often have varying side effects depending on what version of Mnemosyne they've been dosed with. Things like headaches, dizziness, fatigue, nausea, irritability, personality shifts, returning fragments of memory (whether familiar to the subject or unfamiliar), and general fuzziness are all common. More dangerous side effects like brain damage are also possible, but nobody in the main cast appears to have had this issue.

Another key side effect appears to be sterility. Explicitly, it's been said that this effects female subjects, but it's possible that the male subjects are also affected by this without it being said. It's not clear at the moment. More than likely, it's the way the drug is made or what it's made with that leads to these effects, but it is apparently rare for a female subject to still be fertile after being dosed.

Additionally, fertile subjects, according to Monica in Chapter 61, may end up with delayed menstrual cycles and begin to ovulate sporadically or far later than anticipated. Moreover, while these subjects may still be fertile, with how their bodies are affected by the drug, they can still struggle to get pregnant at all. Monica has said it could take a "myriad of tries" before one gets pregnant, or it could happen rather quickly, like in Sienna's case, who got pregnant rather quickly after emerging in the facility.

There have been instances of other side effects being regular or incurable, as in Six's case. In her video feed, she was shown to have an extremely painful reaction to seeing Gale before they altered their appearance. While she does not have this reaction any longer, Six has gone on record saying that she gets frequent headaches, and must be given medicine to help her.

## Boosters

Subjects injected with Mnemosyne receive (at least) tri-weekly injections that serve as "booster" shots, and this is something told to Ten throughout some earlier chapters of the story. It's not entirely clear what the purpose of these shots are, or what they are (much of it was speculated by Five and Six in Chapter 29), but these have a myriad of effects on subjects upon dosage. Things like long-lasting grogginess, nausea, dizziness, brain fog, confusion, and lack of motor function are temporary, but subsist for a few days.

Usually, the booster shot leads to the subject being rendered immobile or unable to do much on their own for a few days, often resulting in their doctors having to be present until their patients can go without supervision. In most cases, the doctors just watch their charges for the minimum amount of time (a day or two), but some doctors have been said to stay the full 3-4 days with their patients (seen in Chapter 50, when Yosuke stayed with Ten). Doctors will also tend to take notes on their patients while observing them, for The Overseer's record.

## In Story

While little is known of Mnemosyne, Ten learns a bit about it later on in the story, especially during her confinement where she is forced to face The Overseer directly. The Overseer apparently prefers to keep everything as secretive as possible, wanting the prisoners only to stay focused on their time at the facility and what's offered there. Ten struggles heavily with the effects of the drug on her psyche and memory nonetheless, often trying to fight against its effects in desperation, as she wants dearly to know who she really is. Throughout the story, she feels close to so many things that present themselves to her either directly or through dreams, yet utterly distant from them at the same time due to her not remembering them. All attempts of hers to bring her memories to light are usually unsuccessful, though some familiar fragments have come naturally to her after being triggered by particular events or phrases, and sometimes simply by chance in her dreams.

The other Numbers, having had the experiences in the facility that they did, have come to accept a lack of knowledge that the still-ambitious Ten has refused to. Constantly, she must be reminded to "let go" for her sake. While the doctors say it to keep her in line, her friends mainly tell her this in worry of her emotional state, and in want of not losing her to the facility, since all current members of the group have had to watch their numbers thin over the course of time.

Mnemosyne remains a mystery to both readers and prisoners alike. All that the Numbers can gather about the drug is what they've experienced of it directly, or have seen in others.

## Effect on Ten

Ten's reaction to the drug is shown to be of interest to The Overseer later on, despite his dislike of having to keep her around given how troublesome she is. Ten, unlike her fellow Numbers, has gaps in memory not only of her life, but of things she's learned. She has been shown numerous times struggling to remember basic things like geographical locations, time periods, definitions, concepts, and even biological functions. Moreover, Ten seems to be one of the very few people in the group who does not have memory of a particular skill, whereas the others have inclinations toward something they used to do in their past, such as Eight with his violin playing, or Blue with her art skills. However, Ten may still have her motor memory, as she instinctively does things like put her hair in a ponytail once, and finds it easy to keep up with people when she dances with them.

Most notably in later chapters, starting from Chapter 80, Ten seems to be able to hear and see things, likely from her past life, in her dreams after pushing herself hard to try remembering, enough to incapacitate her to a concerning degree. After this chapter, she regularly has dreams or haunting auditory hallucinations concerning the voice of a woman she does not know saying things to others, or calling out to Ten. However, despite repeatedly being exposed to these things after her incident, Ten cannot remember anything at all. The Overseer remarks that this is necessary to be studied, and seems to think that this marks a turning point in his drug's creation, as Ten is one of the first of his subjects to not be able to make any connections to her memory or past even if pieces of it seem to be popping up in her head. Other subjects, he's noted, have at least remembered something after a while (if not immediately), but it's not clear whether this is or has yet been the case for the other Numbers too.

## Creation

Currently, nothing is known about Mnemosyne's creation, or what its purpose is beyond simply "memory erasure/suppression". All that is known is that The Overseer has dedicated himself to studying its effects on collected subjects. Though there have been some instances mentioned of multiple versions of Mnemosyne existing, it's not clear what version of the drug is being tested now, nor what versions of the drug each Number has received, nor how effective those versions are.

## Trivia

* Mnemosyne is a working title for The Overseer's drug. It is the name of the Greek goddess of memory, Mnemosyne: mother of the nine Muses.
* Strangely, despite his distaste for the women he surrounds himself with and their associated tendencies, The Overseer chose to give the drug the name of a prominent goddess.
* Despite the drug's name starting with "M", the abbreviation leans on the phonetic syllables of the name. Mnemosyne thus becomes NMSNE.