Every character in Thaumerica knows two languages by default: (1) the native language of their home region and (2) Westerling Sign.
In Upper Thaumerica, the main regional languages are Eastronian (Eastron), Lakese (Lake Countries), Southlandish (Southlands), and Westerling Speech (The West). You can probably guess where most of these regions lie in relation to each other. Each language has its dialects, but those dialects are mutually intelligible.
Westerling Sign (not to be confused with Westerling Speech) is a trade sign language from the West. Everyone in Upper Thaumerica knows it at least well enough to ask about the quality of goods and haggle over prices with strange merchants in the market square, and if you don’t have any other language in common then you can at least converse in Westerling Sign. Because it requires the use of your hands, Westerling Sign is not just a common language but an inherently de-escalatory one. You must sheathe your sword and put down your shield in order to free up your hands, which is why it is actually the preferred language in some places.
Most Thaumerican languages use geographic directions (north, east, south, west) much more than, and sometimes entirely in place of, egocentric directions (forward, right, backward, left).
Other languages an adventurer might want to know:
- Borderer. You can get along just speaking Lakese in Incantucky, or Southlandish in Tennesseer, but the dialects of the southern Lake Countries and the northern Southlands have intermingled with each other as much as they have with the other dialects of their respective regions. Now, it’s possible to just have the languages Lakese and Southlandish and be done with it, but picking up Borderer is worthwhile because it marks you as a kind of insider to the Border Regions: either you grew up here or you put in the effort to learn, and both of those merit respect.
- Gobble. Goblinism is contagious, and it warps the language in a semi-predictable fashion, such that it’s possible to speak of “Lakese Gobble” and “Southlandish Gobble.” You’ll need the root language, too (i.e. you can’t understand Lakese Gobble without knowing Lakese), but if you have both of these things then you can be “eloquent” in a way that non-goblins rarely are.
- Knock. Deep below the skin of the world, light is precious and you cannot be sure of having it. In a place with such strange beings, there are many senses which are had by one kind of creature but only in a limited form, or not at all, but many others. Everyone has a sense of touch, however, and so the people of the dark created a language which requires only that you be able to touch the other party and feel when they touch you. Knocking words are extremely dense: a single “hapteme” conveys information not just from the direction, length, and shape of a stroke but by its pressure, and a stroke which goes from soft brush to forceful press is not the same as one which goes from forceful press to soft brush.
- Luciferine. The devils of Hell are beings of light, partially concealed though that light may be beneath their shadowy armor, and devils prefer to communicate by forming glyphs on their bodies. To “speak” Luciferine is to be able to write it, but doing so is complicated because it is not just the shape of a glyph which conveys information, but its color and luminosity. Interestingly, Luciferine is spoken fluently by many of the more powerful (and more distant) gods, but speculation on this matter tends to upset both gods and devils.
- On-Off. Not every rational being has eyes or ears or a mouth, but everyone has some way to perceive the actions of any other given being, whether they are seeing tentacle-signs or hearing sounds or smelling “pheromemes.” On-Off, which is “spoken” by all interplanetary travelers, is both a binary language (you lift and lower your right hand, they alternate between screeches and hollers) and a set of ritual behaviors for determining (1) whether someone is a rational being or a brute beast and (2) how each party can perceive and be perceived.
- Palattois: There is no “Thieves’ Cant” that is universally known among all thieves, but Palattois, the secret argot of the Pigment Mafia, almost qualifies. It is a melange of languages, many of them belong to Empires Beyond the Sea—Baioccocoa, Grammarian, Sous-Solar, and so on—and extended metaphors and multilingual wordplay, and is understandably difficult to learn. Palattois has many words for the acquisition, appraisal, and selling of illicit goods, of course, but also, thanks to the unique occupation of the Pigment Mafiosi, a vocabulary that is not just figuratively but literally colorful. If there is a shade of color in the world, then there is surely a word for it in Palattois.
- Rattle. The undead cannot depend on having tongues or throats or even fingers, so liches, necromancers, and their servants most often communicate in this click language, whose distinctive sounds can be made by the gnashing of teeth or the clacking of bones as easily as by any mortal speaker.
- Sous-Solar. The language of Sous-Sol, one of the Empires Beyond the Sea. As far as “would-be colonizers colonizers of Thaumerica” go, they were more successful than most, and separate but mutually intelligible dialects of Sous-Solar can be found in Louwitchiana and the Denial of Bells. Sous-Solar is complex, passionate, and vivid, which makes the language perfect for a nation of artists and romantics, but when speaking Sous-Solar it is difficult to communicate in a detached or clinical manner, or to hold back from starting an argument. There are many ways to describe how you feel, but fewer to describe what is.
- Swordsong. Some say that the pen is mightier than the sword. While this is not strictly true, it serves well as a metaphor. Those who know Swordsong can speak with blades as though they were rational beings. Blades appear to have personalities, and there seems to be a correlation between the type of blade that it is and the personality that it has. Broadswords are pompous, whittling knives are patient and attentive to details, etc. Edgeless “swords” like the foil are cognizant but scream obscenities and heap abuse upon anyone who tries to communicate with them.
- Tiamatian. The dragons of Phaeton keep their own counsel. To speak is to breathe, and the breath of a dragon has been sufficient to fell a kingdom on more than one occasion. Though dragons can make use of other languages, they communicate most readily by using their breath weapons: one who is bathed in their fire or struck by their lightning is also being spoken to, however painful the experience may be. Each breath weapon is a (mutually intelligible) dialect, and a dragon who knows multiple dialects of Tiamatian has multiple breath weapons. It is, obviously, difficult for non-dragons to speak Tiamatian (though a Potion of Fire Breathing or the like can help) but it is possible for them to understand it. There is no written form, or at least none which the dragons have seen fit to share.
Rattle is strongly derived from Gus L.’s Foul. Like, it’s 90% just a rewrite of Foul. The first couple of lines from Swordsong, and the concept itself, come from Vayra’s Mountain at the End of the World setting.
Westerling Sign is inspired by Plains Indian Sign Language. Knock is a form of tactile signing and, while I didn’t take anything specifically from it, you should check out the Lorm alphabet because it’s neat (come to think of it, maybe I should have used the name “Loam”).
If I gave special benefits to each language, then Tiamatian would let you give a breath weapon at the cost of hurting yourself every time you use it (you may be able to produce fire, but that doesn’t mean your lungs and throat can handle it!).