"A lead plaque incised, carefully, with Correspondence sigils. Not too many. Apparently even lead can burn."[1]

The Correspondence
The Correspondence is a mysterious language of unknown provenance, known for its effects on the mind and its high flammability. It is related to the freezing Discordance, another language of a perplexing nature.
Surface-Level Details[]
"It's much safer to keep Correspondence letters on lead sheets than on paper. But still, your study is becoming a danger to public health and sanity."[1]

Almost never remembered
The Correspondence is an esoteric form of writing that often consists of complex sigils or pictograms.[1] It is extremely notorious for being hazardous to both the mind and the body; the heat generated from the sigils can scorch an observer's eyebrows clean off just from studying it too closely, to say nothing of the horrifying secrets that now swim through their foolhardy mind.[2] Due its high flammability, it is often inscribed on lead plaques for study,[1] though fireproof paper is sometimes employed as well.[3] It's also occasionally graffitied on the walls of Fallen London, causing public discontent,[4] and such acts of vandalism are often dealt with by the Special Constables.[5]
Besides the occasional scribblings of the lost or confused,[6] this strange language can be found in many locations throughout the Neath: from the dark spires of the Bazaar,[7] to the furthest corners of the Unterzee, including the skin of the Dawn Machine and the stones near the Avid Horizon.[8][9] It can commonly be seen in several places across the High Wilderness as well, such as at the Most Serene Mausoleum,[10] the chaotic region of Pan,[11] and other odd corners of the sky.
There is much rumor and hearsay surrounding the Correspondence, and most daren't study it beyond a passing glance.[12] Approaching it without due caution may result in injuries, terror, nightmares, a trip to the slow boat, a permanent reservation at the Royal Bethlehem Hotel... or a lifelong ban from the library.[13]
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"Menelaus? Raffles? The Third City? What on earth?"[12] There's quite a bit of rumor and hearsay about the Correspondence that circulates throughout Fallen London, as listed below. Not all of it is true, but it's not all completely false either.[12] They say it's the key that opens Mr Stones' vaults. They say it's concealed in Mr Pages' library. They say it's the only way down here you can ever see starlight.[14] They say it's a gate that opens in the stalactites behind Wolfstack Docks. They say you can see it in Mrs Plenty's mirrors. They say it's the only sure way to tell the weight of your soul.[14] They say it's a series of confidential negotiations between the Masters and a devil of some note. They say it comprises the billets-doux written by Jack-of-Smiles to the Traitor Empress. They say it's the letter the Pope wrote, the one without which Rome would have been the Fourth City. They say if you read it your eyes boil and your hair turns the white of old ice. They say it's written on slate in the blood of poisoned bats.[14] They say it's the language the bats speak. They say the Snuffer wrote it on the outside walls of New Newgate. They say the Topsy King learnt it, and that's why you can never understand a bloody word he says.[14] They say it's the letters that Helen wrote to Menelaus in the years of her imprisonment. They say it's the letters Raffles wrote about the Cat that never were published. They say it's the last accounts of the last days of the Third City, strung in beads on cord in a code no-one living understands...[14] They say it's the only map of all the Unterzee, scratched on the keystone of the Neath. They say it predicts every price change in the Bazaar for the next hundred years. They say it's a script that you cannot write and live. They say every piece of deep amber has a fragment of the Correspondence at its heart.[14] They say it's the map that connects every glimmer of moonish light to a star. They say it's the key that unlocks the secrets of bat-flights. They say it's a trap that someone found inscribed on a wall in the First City, and if you decode its complicated patterns you inevitably decide you're God, to the considerable detriment of your social life.[14] They say it's the mathematics of Hell. They say it's the geography of Time. They say it was invented wholesale by a honey-sipper sitting giggling in a cramped and filthy room on Hollow Street, and it's been driving gullible scholars insane ever since.[14] They say only the Brass Embassy knows.[14] |
Scholars of the Correspondence[]
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"There are some things we were not meant to know, they say. But you wouldn't be down here if you took that seriously."
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"A new one! What does it mean? 'Tracks in the illimitable void?' Is it that character that translated as an emotion somewhere between love and academic excitement? Or the one that seems to mean 'bad-tempered gas?' In any case, it's meat for your researches."[15]

232.778 degrees Celsius.
Those clever or foolhardy enough to study the Correspondence in detail are called Scholars of the Correspondence.[16] These smoldering academics are few in number,[17] and have a tendency to frantically study any sigils they can get their eyes on, safety and sanity notwithstanding.[18] They commonly frequent the Forgotten Quarter, as it is littered with searing artifacts.[19] The University also has an unnamed department dedicated to studying the Correspondence, though they prefer to practice restraint when handling the language, and shy away from handling the Correspondence directly.[20] It is considered extremely dangerous to study this language on the Surface, as it is outside the safe confines of the Neath.[21]

A Semiotic Monocle.
Unsurprisingly, studying the Correspondence can be difficult even for the experienced academic. Works regarding the Correspondence are often fiercely hoarded by collectors or are outright destroyed by the Ministry of Public Decency,[22] and lengthy discussions regarding the Correspondence in detail can be extremely detrimental to all parties involved.[23] In fact, just thinking about the Correspondence can result in feelings of being scorched.[24] Thus, common methods for studying the Correspondence include direct field research: learning new sigils, studying uncovered sigils in detail,[15] or sleeping on Correspondence-inscribed artifacts.[25] Scholars also use unique devices, such as Semiotic Monocles, to study the Correspondence safely,[26] and especially advanced academics may experiment with lead Correspondence Plaques, at the presumed detriment of their long-term health.[21]
The Language of Stars[]
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"Are you sure you want to know this?"
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"How interesting. You speak the language of Xanadu. A doubly impressive achievement when one considers the comparative lightness of your cranial scarring. Perhaps you will travel to converse with the stars themselves."[27]

The Correspondence is the language of the Judgements - the stars, like the Sun.[27] These sky-gods use the Correspondence to communicate amongst themselves, using Messengers like the Bazaar and the now-deceased House of Rods and Chains to correspond with one another,[28][29] and to ensure that their messages are not forgotten, Messengers inscribe the Correspondence on their carapaces.[30][31] Correspondence sigils can also manifest directly on a star's surface, dimming their brightness somewhat and appearing very similar to sunspots.[32]
Lawful Light[]
"Sunlight is - in certain senses literally, quite literally, law. Without sunlight, the earth would spin off into space. And the absence of sunlight down here means the absence of a dozen laws. Death operates unreliably (though more reliably on the zee, as you know). Geography is uncertain and shifting. And dreams - dreams - "[33]
"Mathematics. Formulae. Principles that dictate how the planets move, how apples fall, how confessions can be compelled. How confessions can be compelled: the same way apples fall, and planets move. Apply the right force. Ask the proper question. The effect will follow the cause. Whoever you interrogate will speak the truth, because in the language that governs the stars, there is only the truth."[34]

Many forms of the Correspondence are in fact a form of law, and Judgements use the Correspondence to enforce and maintain their celestial principles.[35][27] Certain manifestations of the Correspondence are indistinguishable from light,[36] so a Judgement's starlight can easily subjugate anything it reaches to its will, with the finality and certainty of a deity.[37] With a single flare, a Judgement can impose on its subjects any law it chooses, including laws that determine the rules of mortality, the stability of geography, the nature of dreams,[33] or even the definition of existence itself.[38]
The forms of law that the Judgments enforce can range from laws defining gravity, to the trajectory of planetary orbits, to the method of proper interrogation, but they all have a core theme at heart: every sigil of celestial law defines a strict cause and an effect, because in celestial law, there is no flexibility or uncertainty; only truth.[39]
Sometimes, the Judgements need active enforcement for certain tasks or interpretations of their laws. To this end, they may create Logoi, living sigils of the Correspondence that are effectively immortal and carry out their duties with fury and gusto.[40]
Applications[]
"It's probably safe to weld Correspondence Plaques to the stove's bottom. After all, the stove is metal; the plaques are metal; if one hasn't caught fire, the other shouldn't. And even if there were a fire, isn't that the idea?"[41]

A Searing Enigma.
As one of the most all-encompassing and versatile languages in the universe, it's not surprising that the Correspondence has a variety of surprisingly practical applications. Naturally, its most obvious use is allowing communication between two highly disparate parties,[42] or convey concepts that cannot be easily explained in lesser tongues.[43]
Unlike most languages, which reflect the world and order thoughts, the Correspondence is capable of shaping the world and composing thoughts of its own accord.[44] The meanings of sigils of the Correspondence that represent concepts can be especially notable, as they can be used to convey certain characteristics onto the objects upon which they're written. For instance, carefully inscribing the Correspondence sigils for "Light" and "Constancy" onto a waxen cylinder can create a candle that never loses its flame.[45][46] Furthermore, the influence of an inscribed sigil may extend far beyond the object on which it was inscribed; the entirety of Langley Hall, for example, is under the influence of an alluring Correspondence sigil seared onto the body of the eponymous Lord Langley, giving the Hall its infamously hypnotic properties.[47]
But sometimes the meaning of the Correspondence isn't as important as the properties of the Correspondence. Naturally, its most well-known property is its ability to generate large amounts of thermal energy, and as such the Correspondence can be used as an extremely powerful heat source. When used correctly, it can also generate a form of smokeless combustion.[48] However, using the Correspondence for this purpose can be dangerous, as the resulting fires can be highly volatile and difficult to control.[49]

The Correspondence's uses go beyond mere communication and esoteric engineering, however. When in the hands of a truly unscrupulous individual, the Correspondence can be used to push the very boundaries of reality. Sigils of the Correspondence can grant false life to flesh, enter dangerous pacts in exchange for service,[50] be used to inflict tremendous amounts of torment on the unwary or unfortunate,[51] or prove useful in other dark quests.[6] In fact, one of the most powerful uses of the Correspondence is its ability to manipulate time, space, and causality. With the right sigils, the Correspondence can untangle space and restore nearby surroundings to a prior state, though of course, such endeavors are no easy task, and may require entire teams of dedicated Correspondents to execute correctly.[52]
Paradoxical[]
"There is no law: that is the law. Heat something, melt it, reshape it. Translate it into something new. Even the truth is mutable. Even the words you're reading aren't the words you're reading now. You scan the last sentence again. It's different. You flip to the index. There is no index. Page numbers change. Your head begins to pound."[34]

The Memento Mori
Even a language as ancient and esoteric as the Correspondence isn't immune to the concept of paradox; there exist self-contradictory, nonsensical, or illogical forms of the Correspondence. These mysterious laws are so paradoxical that they barely even resemble "laws" at all, but they burn all the same, and they embody the inherent mutability of language, truth, and the universe.[53]
As such, sigils of the Correspondence are as capable of distorting the universe as structuring it; for example, they can be used to encode Treacheries, or critical fractures in the order of the world, when properly "trained into defiance".[54][55] Thus, the Correspondence is a crucial tool in the study of Red Science,[56] the practice of breaking old chains and forging new links.[57]
Practitioners[]
"A jolly devil approaches you with a wager on the outcome of the match. If Benthic XI win, you receive an ancient text concerning the Correspondence. If the Brass Embassy Ladies win, you must publicly punch the Summerset chaplain."[58]

A Devil.
Besides humans and the Judgements, there exist many wielders of the Correspondence from all corners of the universe. The Masters of the Bazaar occasionally speak it among themselves,[59] and the Lorn-Flukes and Mt Nomad are capable of weaponizing it to devastating effect.[60][61] Mysteriously, eyes blessed by the Correspondence are also often sought by spider-councils.[62]
Devils are also very knowledgeable of the Correspondence,[63] and they utilize it in some of their highly advanced technologies, such as in their reliable devil-killing execution devices.[64]
Correspondents[]
"The Correspondent writes with a pen of fire and a hand of adamant. No topic is beyond his consideration, no subject too fundamental or necessary to be critiqued. He has, with a single essay, destroyed a religion, started a war, or shaken the earth."[43]

A Pot of Violant Ink.
Correspondents are professionals in the Correspondence who specialize in world-changing academics.[43] These individuals tackle topics no one dare question, or topics typically taken for granted, and flip them on their heads, causing upheavals across certain circles and outrage among others. Unfortunately, their publications are often considered to be too advanced for the average reader, so they're unpopular to most audiences.[43] Correspondents are also experts in wielding the Correspondence for their own ends, such as to convey their reputation,[65] make demands,[66] play politics, or other tremendous feats.[43]
The ink Correspondents prefer to use is violant, the color of troublesome but necessary connections,[67] as violant ink is the one of the best inks for conveying the connection between meaning and symbol.[68] Apparently, it tastes like pitch with a hint of tears.[67]
Spelling and Grammar[]
"You walk through the city to the glistening black spires of the Bazaar. Your studies have advanced to the point that you understand a little of the grammar of the Correspondence."[69]
Like all languages, the Correspondence has rules regarding grammar, spelling, and structure, but these rules can be unintuitive or hard to understand.[69]
Sigils and Sentences[]
"Some sigils are known and frequently attested. Some can be guessed, assembled from other marks. Some are hapax legomera, seen once in the corpus and never again. And some marks can only be definitely identified as Correspondence when you write them on a page and discover that they burn."[70]

Eight sigils?
Certain sigils of the Correspondence are well-known and frequently prove useful, while others are hapax legomera, meaning they're seen once and never used anywhere else. Notably, some sigils can only be identified as such by their tendency to burn.[70] Sigils can be constructed from scratch by assembling them from other marks,[70] while others can be created from several sigils overlaid on top of one another.[71] Certain sigils can also act as root-sigils, from which other sigils are derived.[72]
Sigils of the Correspondence are usually interpreted as having one meaning, but sometimes, they can take on several meanings depending on the context. For instance, the Pansekritis is a Logos that can mean "Eternal dominion", "Everything in its place", or even "No drop-in meetings permitted".[73] Furthermore, certain sigils of the Correspondence may take on different meanings based on their orientation; for example, one sigil means "to circle a point without reaching the point" when turned sideways, and "always looking toward the horizon" when upside-down.[74] Correspondence sigils that are reflected in Parabola are described as "left-handed" and said to take on a "darker meaning", though the precise implications of this are unknown.[75]
Sentences of the Correspondence can sometimes be hard to define; sigils of the Correspondence that are near one another can sometimes be unrelated to one another, and sentences can span long distances and be spaced far apart.[76] However, only a maximum of six sigils can be written safely on a single surface; seven sigils tend to burst into flame and destroy the surface they're written on.[77]
Other Rules[]
"In tandem, at the striking of the clock, four Correspondents write on the paving, 'return from exile', with the punctuation mark that renders the sigil into a command."[78]

A Starstone Demark.
Punctuation in the Correspondence can be especially useful for parsing or using the Correspondence accurately. A certain punctuation mark can render a sigil into a command,[79] and mysterious stones called Starstone Demarks are said to act as punctuation in the Correspondence, as well as weapons, tokens, and punchlines.[80]
The Correspondence is capable of encoding idioms and accents,[81][82] and its also susceptible to its own form of "slang": unique, external forms of language disguised with celestial syntax that do not fit standard Correspondence, but superficially appear to.[83]
The Correspondence is also capable of representing numbers, quantities, and tallies, especially large ones.[84][85] Furthermore, it has applications in esoteric forms of math and strange equations, but it may also produce unpredictable results.[86]
Names in the Correspondence are special; they're designated with a unique superscript,[87] and have strange interactions when inserted into equations.[88] Certain names, such as the Name-Which-Burns, are represented with seven letters, and these names tend to burn.[89]
Sequences and Mediums[]
"A law is a sequence of words, and words are simply meanings translated: by lines on a page, by sounds in a mouth, by movements across a ballroom. Or a cricket field. Correspondence blazes in your brain."[34]

Cricket, anyone?
Writing the Correspondence is in fact only one of the many ways to express it. It can be conveyed through speech,[59] and when spoken, it may take on the form of light,[36] or form sigils in the air. However, speaking the Correspondence can be extremely scarring,[90] even destroying a speaker's voice and filling their lungs with blood.[91]
Devils, such as those of the Well of the Wolf, are skilled in using song and dance to convey the Correspondence. Their dances can form patterns resembling the Correspondence, and they may sing hymns to convey inflection.[92] Musical instruments can also convey sigils of the Correspondence, but such a performance may require strange instruments and stage arrangements, such as glass drums or bassoon players that hang from the ceiling - to say nothing of the chaos that may ensue.[93]
In fact, any sequence of defined events, from writing, speech, dance, or any other action, can be a form of the Correspondence, as "actions" are sequences of events, "laws" are sequences of words, and "words" are simply meanings translated into a suitable medium.[94] Thus, even something as unorthodox as cricket can serve as a medium for the Correspondence: the bat, a pen; the ball, a punctuation mark; and the universe, the paper.[95]
Compilations[]
"With pen, paper, and a hardback copy of Dolford's Compilation, you subject your transcription to a merciless interrogation. You use a magnifying glass at several points, until it melts entirely."[96]
There exist several compilations of the Correspondence, and given their contents, many of them need to be handled with care. One such compendium is the Gulbahar Redaction, a four-volume book consisting of sigils deemed forbidden by the Ministry of Public Decency.[97] Another compilation is titled Guttering Embers: a Study of Three Abandoned Branches of the Chiswick-Myers Semagramic Tree.[98] Yet another compilation is the Dolford Compilation, which notably contains designations for dangerous sigils, called Regrettable, and includes threat levels for them, the most dangerous of which are termed conflagratory.[99]
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"Thank you, captain. How marvellous. It ought to be classified with the Regretables in the Dolford Compilation, I think. The impact that destroys, the fire that burns bright. For some, there is no surrender. Very good, captain. Here, your reward. I'm more than happy to do business with you from now on."[100] Below is a gallery of all known images containing Correspondence sigils from Fallen London, Sunless Sea, and Sunless Skies. The Imagined Contents of a Span of Time Between When an Event was Supposed to Occur, and When it Finally Did |
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"The sign does not appear in any of the common collections, nor in your more obscure compendia. You meet with a Supposedly Retired Professor. His office is gloomy with walnut and pipe smoke. He explains at exhaustive length that he has never seen the sign before. Furthermore, he knows absolutely nothing about a list of prohibited Correspondence sigils maintained by a Senior Auditor at the Ministry of Public Decency."[97] Below is a list of all known Correspondence sigils and sentences from Fallen London, Sunless Sea, and Sunless Skies. As with any reference text, there's a chance this compilation may be incomplete or outdated.
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Real-Life Inspirations[]
Correspondence tablets may have been inspired by Greco-Roman curse tablets, which were pieces of lead or pewter inscribed with curses against specific people (e.g. thieves).[171] It's possible that they were also inspired by cuneiform, Egyptian hieroglyphics, or Mayan hieroglyphics, all three of which have strong ties to Fallen London's story as the writing systems of the first three fallen cities.
The sigil 'The act of drowning your sister to be with the one she loves, although you do not share that love' is a reference to the folksong The Twa Sisters.
References[]
Special thanks to 0bsidianFire and WaltzingOphidian.