UNIVERSE - _{A small, self-contained reality which is distinct from other realities and made separate by a "universal membrane". May also be referred to as an AU (alternate universe), or world (primarily by humans). May be incorrectly referred to as an AT (alternate timeline) — a term for separate realities coming to pass chronologically inside of a single universe.}

MULTIVERSE - _{Any collection of distinct universes which itself is distinct from other collections, and made separate by a "multiversal wall ". Untraversable by normal means.}

PRIME - _{The first universe to develop in any multiverse. PRIME's code acts as a blueprint for all future AUs, which will continue to diverge more (and have more chances for anomalies) as they are born farther away. Also known as "the multiversal nucleus" in academic circles.}

MULTIVERSE TAU - _{The 19th known multiverse. Also known as M-TAU or just TAU.}

(THE) UNDERGROUND - _{A grand system of caverns found under Mt. Ebott, which serves as home and prison to monsterkind in most AUs. The actual location of "Ebott" — and therefore its respective Underground — varies by universe, which in turn affects monsterkind's culture.}

(THE) CORE - _{The thermomagical reactor responsible for supplying the Underground with power. Most versions of monsterkind become dependent on the Core's output to farm the magic-rich crops they need to survive. In many universes, it is an anomalous object, with both "always existed" and "recently invented by the previous royal scientist" being true.}

INCODE - _{An entity which lives inside (or else does not regularly leave) a universe. May also refer to the "living area" (main planetary surface) of a universe predominantly occupied by incodes — I.E.: "an incode world". Incodes are more heavily affected by a world's rules.}

OUTCODE - _{An entity which lives outside (or else regularly leaves) a universe. May also refer to the "living area" (main planetary surface) of a universe predominantly occupied by outcodes — I.E.: "an outcode world". Outcodes may be able to comprehend things incodes can't.}

CODE - _{The information that makes up every piece of reality. Something of a misnomer; bears more resemblance to DNA than any language of computer code. Notoriously difficult to parse.}

CODE RADIATION - _{A form of non-ionizing particle radiation which is released by decomposing code. Not particularly dangerous in small doses.}

CODE MUTATION - _{A phenomena where regularly traveling outcodes, through regular exposure to the code radiation found in the VOID, slowly begin to develop physiological changes. Such changes are usually subtle, relatively harmless, and take several years to begin manifesting outwardly. May be called "code corruption", especially if said changes are life-altering.}

VOID - _{The empty space between universes. Moderate code radiation.}

ANTIVOID - _{The empty space between multiverses. Very high code radiation.}

THE WAR BETWEEN HUMANS AND MONSTERS - _{In most AUs, the deciding event that leads to the imprisonment of monsters under Mt. Ebott. More rarely, it may lead to the imprisonment of humanity or to monsterkind's extinction. The near-extinction of magi always follows it.}

(POST-)PACIFIST/NEUTRAL/GENOCIDE - _{Classifications for the most common ways that monsterkind exits (or does not exit) their respective Underground. Typically triggered and/or brought to fruition by the Catalyst. The actions that bring a "route" to its climax are referred to as a "run"; ie: "doing a neutral run", "post-neutral run", "the neutral route".}

MAGIC-USER - _{A generic umbrella term for any sentient entity that can consciously burn mana for the use of magic, regardless of species. If it's not sentient, it's instead a cursed or charmed object, which are comparable to simple computers in function and limitation.}

MUNDANE - _{Any entity which cannot use magic, or object which does not contain mana.}

HUMAN - _{A sentient ape of the extant species Homo sapiens. Their physical nature makes them somewhat nonreactive to magic, and more resilient than creatures who are adept at magic-use.}

MAGE/MAGUS/MAGI _{⁽¹⁾ - A human born with a physical, genetically-dominant irregularity of the SOUL which allows them to burn mana for the use of magic, especially for the formation of constructs. Magi can be extremely powerful and long-lived, but typically trade this power for lifelong physical health problems. Also known as an "active" magic-user. ⁽²⁾}

MAGE LINEAGE - _{Any family comprised of more than 90% non-latent magi. ⁽³⁾ Aptitudes for certain abilities typically run dominantly — for example, specializing in healing magic or fire magic, but not both. More specific abilities generally mean greater power but poorer health. By contrast, a "bastard" magus will likely be weaker, but healthier & less limited.}

WITCH _{⁽⁴⁾ - A subset of magus that is capable of limited magic use, but not to such an extent as to be able to form constructs. A magus may "start" as a witch if their abilities take a long time to develop (or else do not awaken naturally); similarly, a magus may once again "become" a witch through sickness, age or injury. Also known as a "passive" magic-user.}

MONSTER - _{Any sentient entity which is not human and has a SOUL. Monster physiology is naturally less solid than a human's (more mana than matter), making them extremely susceptible to any magical or emotional influence. Said physiology, however, tends to make them naturally adept at magic use, to such an extent that magic defines their cultures.}

BOSS MONSTER - _{An uncommon subtype of monster which is differentiated by being especially magically powerful and extremely long-lived, with SOULS that can persist after death. Any monster has a small chance to be born as a Boss, which raises significantly if one or both of its parents are Bosses. Some monsters can also temporarily become Bosses under duress.}

HYBRID - _{The offspring of a monster and human. Can only result in one of two possible first-generation hybrids, which will themselves be infertile.}

ALTERNATE - _{Any iteration of a certain entity which exists in more than one universe, typically at the same or very similar (relative) time. Alternates born or created closer to PRIME tend to more closely resemble their "original" iteration, or "sourcecode" ⁽⁵⁾.}

(THE) CATALYST - _{The entity which triggers the inciting events of a universe's timeline, if any exist. Depending on said events' requirements, the Catalyst is a "role" which can be filled by any entity — however, it is usually a human child known as Chara or Frisk.}

GOD(S) - _{An entity with significant control over a specific force or concept. Typically, such forms of godhood are "roles" that any powerful-enough entity could fill — thus, most gods are capable of dying and being replaced, even if it would be temporarily catastrophic.}

PERSONIFICATION(S) - _{An entity which is the "living embodiment" of a specific force or concept. A personification's existence is inextricably tied to its domain, making the entity impossible to kill without also destroying the concept it represents — or vice versa. They will be responsible for maintaining a balance related to their domain, and may do so unconsciously or by instinct. May also be known as "titans" or "primordial deities".}

primordial organ - _{any of the first superorganisms to develop in an infant multiverse, serving as sort of proto-personifications to regulate one or more of the multiverse's early Balances. The death of a multiverse's primordial organs (and subsequent replacement by the corresponding personifications) roughly marks a multiverse's entrance into "adulthood".}

CREATOR(S) - _{Humans who receive limited precognitive visions of entities in other universes, and who may be able to influence limited changes in the worlds they dream of. To avoid potentially cataclysmic feedback, universes suspected to hold Creators are off-limits. Near-copies of creator universes which lack the same influence are called meta universes.}

DESTROYER(S) - _{Entities aiming either to destroy parts of the multiverse, or to spread fear and misery throughout it. Typically outcodes. Their methods and motivations vary.}

MANA - _{A dense, volatile, highly adaptive form of energy which enables an entity's emotional function, memory and willpower.}

MAGIC - _{Any act of consciously burning mana with the intention of altering a physical or metaphysical aspect of reality. Many different types of magic exist, loosely grouped under constructs (the conscious condensing of mana into a physical shape) and spells (anything that isn't a construct). Use of the term "spell" is more common among humans; monsters tend to call the same concept "magic" — IE: "healing spell" (human) vs. "healing magic" (monster).}

BULLET - _{A type of low-mana construct exclusively meant for throwing, typically as a hands-free offensive projectile. Extremely common amongst monsters, and thus popular in Encounters.}

BARRIER - _{A defensive magical construct. Barrier spells are a relatively common skill amongst magi, but are almost never practiced to proficiency given the popularity of offensive magics. Monsters cannot create "true" barriers, but can mimic them using lesser constructs.}

ENCOUNTER - _{A form of communication primarily used by monsters, where two entities use magic to isolate themselves from their surroundings and engage in an turn-based mock-battle. Encounters may involve choreographed displays of magic, verbal sparring or controlled hits from bullets, which, under normal circumstances, are not meant to do serious damage.}

(MONSTER) DUST - _{The fine, powdery byproduct left behind after a monster dies. Common funeral rites are to spread the dust over something the monster loved. More rarely, monsters may participate in ritual cannibalism, incorporating the dust into food meant to sustain the community. In some worlds, this concept inspires "supplements" meant to create hybrid food.}

MONSTER FOOD/MAGIC FOOD - _{Food that is either extremely rich in or comprised primarily of mana. Typically created by seeding mana into mundane crop plants — which, unlike animals, can retain most of their rigidity even with high mana content — and then preparing the resulting produce normally. Because of this, most versions of monsterkind are vegetarian.}

HYBRID FOOD - _{Physical food (or "human food") with a mana-count that has been artificially raised by the addition of a third-party magical ingredient, such as a dust-based additive. Given that neither species can fully survive on the diet of the other, hybrid food typically serves as a social or accessibility tool, and is not meant to be a permanent dietary staple.}

(OBJECT) OF POWER - _{An object which comes to act as a nucleus to create and store magic like a SOUL would. Extremely rare; typically quite powerful. How they come to be is unknown.}

SOUL - _{The culmination of one's being. Produces and stores some amount of mana, even if the entity it belongs to is not a magic-user. May carry a color which signifies the entity's dominant trait, if any exist — generally, the more pure this color, the more pure the trait.}

SOUL STATE - _{A type of temporary status effect applied to the SOUL through contact with specialized constructs. Like all forms of magic, SOUL STATES can be helpful or harmful depending on the caster's intentions. Typically, only boss monsters can apply them.}

SOUL SICKNESS - _{Any type of magical malady. Though SOUL sicknesses have long been thought to be exclusively caused by trauma or injury, as more universes see integration between monsters and modern human medicine, there is mounting evidence of a genetic aspect.}

SOUL SEX - _{Any form of sexual activity involving the SOULS of two or more entities. This is the primary method of reproduction in monsters, who are typically biologically sexless and present next to no distinct sexual dimorphism. (Not to be confused with gender identity or expression, where different types of monsters may or may not superficially resemble humans.)}

ECTO-CONSTRUCTS - _{A mild form of magical transmutation where specialized constructs are formed to mimic the sexual characteristics of humans, for use in gender expression or alternative intercourse — however, given how mana-intensive they are, casual use is typically limited to bosses. They may also be involved in later stages of SOUL reproduction if the carrying parent needs to manifest a layer of "ecto flesh" to protect and nurture the SOULING.}

STATS - _{Numerical representations of information about an entity's health or abilities, originally for use in encounters. Average stats vary greatly between different groups, and between the incode and outcode versions of those groups. Popular stats include HP ⁽¹⁾ (Hit Points/Hope), LV (LOVE/Levels of Violence), DF (Defense), AT (Attack), and MP (Mana Points).}

LEYLINE(S) - _{Invisible tracks which circulate magic through the body. Found in (and are essential to) most living flora and fauna, but are much more prominent in magic-users. For monsters especially, it functions as both the circulatory and nervous system.}

AURA - _{The exhaust of burned mana as it leaves the body, typically invisible to the naked eye. Auras carry various types of information which, at least to a small extent, most creatures can sense. If an entity is especially sensitive to it, it is known as an Empath.}

DETERMINATION/DT - _{A type of mana which gives an entity, among other things, the will to exist after death. Typically found in high quantities in humans but less in monsters, who are physiologically reactive to it. A monster who overdoses on DETERMINATION usually melts.}

DT ABILITIES - _{Any of a set of powerful, extremely rare magical abilities which can warp the natural world in ways normal magic cannot. The most common of these abilities are the creation of SAVE POINTS, or anchors in an AU's timeline. Generally, the returning to a recent save point — manually or upon death — is called a LOAD, the returning to a universe's first save point is called a RESET, and an extremely localized LOAD may be called a REFUSE.}

BALANCE - _{May refer to the BALANCE OF MAGIC, BALANCE OF LIFE, or the BALANCE OF EMOTION. If any of these fall out of alignment, M-TAU will die.}

nightmare's pantheon - _{a small but powerful terrorist group seeking to spread negativity throughout multiverse tau, led by an entity known as Nightmare. Its members include the "Sanses" from TAU-HT 821147518, TAU-XT-0, TAU-DUT 1854189147 and TAU-SN 1452345112, and more recently, a magus from TAU-PRIME 1821914. The group's exact goals are otherwise unknown.}

the stars - _{a small anti-terrorist group originally formed to to spread positivity and to provide relief efforts to universes affected by nightmare, led by an entity known as Dream. Its only member is the "Sans" from TAU-US 69181920, save temporary alignments with the creation mechanism, and occasionally unofficial volunteer work from TAU-ΩT's refugees.}

the leukocyte - _{aⁿ\ </EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE RROR>}

the creation mechanism - _{a powerful but enigmatic entity known as Ink, who acts as M-TAU's personification of creation, seeking out areas where universes will soon be naturally born and heavily assisting in their birth. His existence (and the nature of his abilities) are theorized to be the vehicle through which Creators receive their precognitive visions.}

the omega timeline (ΩT) - _{a closed pocket of ANTIVOID converted into a safe haven by an anomalous entity known as CORE. Most entities only come to live in this place because their original worlds were destroyed or made uninhabitable. Though it's not technically a world, its classification (for the few entities born inside of it) is officially TAU-ΩT.}

X!GASTER - _{The entity who created TAU-XT-0. His self-proclaimed goal is to create a single "perfect" universe through the copying and editing of code, then to destroy all that remains.}

Who are you?
_{My name is Keegan — he/they, 23, disabled mixed-race gay man and Mexican refugee. I've quietly been a fan of Undertale since the beginning, and for longer still I've loved to think about how fantasy & sci-fi subjects could "work" in real life without losing their charm. :>}

Did you make the art featured here?
_{Yes! All the writing and art is by me, and all the stock images are from Pexels!}

What do you use to draw?
_{A mix of Clip Studio Paint and Krita, mostly! The ratio depends on the look I'm going for.}

I don't see credit for these AUs! Where is the credit?!
_{Don't worry — linked credit is given inside each profile, front and center in "basics". Moreover, all of my fanart is tagged under the appropriate character tags on Tumblr, in addition to the "multiverse tau" tag so that people can track my fanart specifically.}

Is there going to be a story?
_{It's more likely that there will be stor-ies, plural, since I work best with shorter prose — especially with unmedicated ADHD and a full-time freelance job. There is, however, a main storyline, and any work done for either of these will be posted about over on Tumblr.}

Can I do fanart, fanfics, etc. inspired by m-tau (or featuring Abaddon?)
<sub>You can! (And I would be flattered!) The story of "Multiverse TAU" features the blend of canon and fanon that I personally prefer with my own dash of worldbuilding mixed in, inspired by the likes of The Ancient Magus' Bride (2017), Soma (2015) & Annihilation (2016). However, at some point I realized that some of the changes I was planning to make were bound to cause confusion — and that the story building up in my head needed a name — which is how M-TAU was born. If you like something I'm doing with one of these characters, you're more than welcome to gather up your favorite bits for your own stories — that's what fandom's all about, IMO!

My one caveat: if you want to write about Abaddon, I would prefer if you waited for me to write & publish a few things featuring them, first, just so that there's actually some form of "canon" characterization for you to refer to. And if you have any questions, you can ask!</sub>

Is Abaddon a self-insert/an OC/your persona?
_{Sort of! He's more accurately a caricature of me — a very simplified, exaggerated reflection with most of my worst traits (and a few of my best) cranked up to 13. To that end, he's far more OC than persona... but in the rare times I need a persona, I tend to use his likeness.}

Is this going to be a romance/shipping story?
_{There's definitely some weird gay QPR type shit in the cards, yeah, but I'm not sure how explicit it will be. Either way, it's not really the focus of the "main" story, so if that's not your jam, you should be able to enjoy it all the same. (Minding the triggers, that is.)}

Will there be smut?
_{I actually have no idea. I don't have any overtly sexual stories planned, but suggestive content/mentions of sex, definitely. To be safe, let's err on the side of caution & say yes.}

Will this story feature any common or major triggers?
<sub>Yes — Multiverse TAU will feature themes of body horror, non-consensual body modification, ego death or alteration, depictions of neurodivergency (including dissociation, PTSD, OCD, ADHD, Autism, TBI(s) ASPD & Schizophrenia), gore, mentions or depictions of cannibalism/man-eating, chronic illness, anti-religious sentiment, occult practice, substance abuse, self-harm, (magical) parasites, mind-control, temporary main-character death/suicide (esp. as an ability mechanic), (past) transphobia, and finally a generous scoop of cosmic horror. Some of these will be explicit. There will also be significant themes of moral ambiguity given that a terrorist group is playing the role of the protagonists, so please moderate accordingly.

To be clear, as well, I do my best to research each subject that appears in M-TAU, especially in the case of mental disorders I myself do not have, but the under-researched and over-stigmatized nature of certain mental disorders means that I could be portraying a lie without realizing it. If you notice that, I invite you to tell me so that I can fix it.</sub>

Do you condone [insert IRL crime or other morally repugnant action here]?
_No.

I have greatly misinterpreted something you said in bad faith. Can I contact you so that you can defend yourself to me and assure me that I'm wrong?
_{You can certainly try, but you'll be ignored, and repeated attempts will get you IP-blocked. I log onto Tumblr to look at fanart, not to engage with people looking for something to hate.}

Why do you sometimes vanish for a long time after posting?
_{I am dirt-sucking poor — like, "constantly on the verge of homelessness", "last meal was multiple days ago" poor — so most of my energy needs to go into trying to make enough money to live. If you want to see more content from me, you can help by commissioning me, or maybe donating a coffee if you don't have the cash or the time for the queue. Or, if you're in a similar boat as I am, maybe consider commenting on something I made; it fuels me immensely!}

Are these profiles complete?
_{For now, yes, but they will inevitably be edited as I spot errors and typos, or else as the information relating to the AU changes and evolves.}

Why Carrd?
_{Apparently there's a section in Toyhou.se's TOS against AU characters; otherwise this project would have been there. (In fact, all of its earlier drafts were held there for ages. Oops!)}