6 Weird uses of "Comprehend Languages"

[1] Language of Dance
You lose the ability to talk, but you emote. This is the language of mimes and anything that dances to get attention. While under the effects of this, you can't cast any other spells, but you gain +2 AC from your ability to read and react to the words of motion. On the plus side, you can now understand giant bees and Swerda, or anything else that communicates through dance.

[2] Language of Magic
You lose the ability to talk normally, but can still cast spells through the strange warbled effect of your incantation-speaking voice. While comprehending magic itself, you can see what spells an enemy magician is about to cast the round beforehand as the energies being to gather around their body in an invisible aura. The DM must tell you what spell(s) the enemy magician has prepared at least one round before using them. Finally, you can understand creatures of pure magic or those creatures from the astral plane if they couldn't already be understood by a regular "Comprehend Languages" spell.

[3] Language of Machines
You lose the ability to speak and cast spells. However, your eyes become incredibly attuned to movements, and connections between objects as well as their apparent weight, composition, and purpose. By simply staring at an exposed collection of gears through a crack in the wall, you can tell the general purpose of a machine by staring at a small amount of its constituent parts. (The "purpose" here is always told in vague terms. Like a machine that shifts the walls of a labyrinth around is described as "it seems like its meant to move heavy weight" and so on).

Secondly, you gain +2 to saves against devices and traps. If you can somehow communicate with the other party members during this spell (or just attack yourself), you can also tell the weak points of various automatons and not!Robots in a fantasy world, granting advantage on attack rolls.

[4] Language of Water
You lose the ability to speak, but only above land. You can still cast spells, but only in the water. Spells come out as big bubbles that have to be popped by something sharp, with the spell being cast wherever the bubble popped. This spell does not grant water breathing. While under the effects of this spell, you can instinctively feel the motions, volume distortions, detiritus, and sound through a body of water. You can tell when a creature that is big enough to display at least a man sized amount of water is drawing near; you can avoid one random encounter while underwater.

[5] Language of Cloth
You lose the ability to speak. You can only cast spells if their target is yourself or directly around yourself/the target of the spell (you billow out your robe to make the spell come out). You gain the ability to understand the stories written in every piece of cloth and along every thread of twine. By looking at people's clothes you can see where they have been recently, and general ideas about their lifestyle. By touching and examining a piece of cloth or fabric you can tell generally where it has come from or who made it. This spell also lets you identify magic items by wearing them and feeling them up, but only magic items made of cloth. Finally, this language lets you see if anyone is hiding something under their clothes by reading the tiniest creases and folds of their outfit when they move and stand. This ability does not work on bottomless bags or bags of holding, since the item is just a gateway to another space.

[6] Language of Winds
You lose the ability to speak and cast spells, but can read the wind. You can gather smells and sounds from farther away; whispers across a city square filter into your ears from a distance, and can tell where and what is causing any given plume of smoke or sudden pillar of dust.

Additionally, by breathing and flowing your breath out in certain sequences, you can make the wind follow your motions. You can produce a stiff breeze to knock over objects, a gale wind to knock away arrows or push people back, or strength/reduce a storm in strength; taking a round, two rounds, or a turn respectively. Once you've used one of these, the wind moves on leaving you with nobody to talk to until the next time you cast this spell. 

20 Sounds to base your Magic Language On

Roll on this table to see what sounds and general feel you should use to make your ancient, magical language sound like. You can connect this to the lore reasons as to why it sounds this bad.

20 Sounds for the basis of your Magic Language

[1] Ancient Sumerian. Lots of grunting, simple words like UMA or ELE.

[2] Hebrew. Yelling “Oy Vey!” when your spells fuck up is not necessary, but highly encouraged.

[3] Ancient Egyptian, or just invoke the names of their Gods since that works too.

[4] Aztec. Lots of q's and unpronounceable nonsense. Cool art though.

[5] Just screaming.

[6] Kulning. Scandinavian cow calling- very fitting for Elvish magic.

[7] Nonsense rhyming-whyming bullshit words. Bibitties and bobbitties.

[8] End all the words in exhaling, hissing consonants, like h's and s's. Use for ancient snake sorcerers.

[9] Say what you want a spell to do and then reverse the tape. Talk backwards.

[10] Sound effects. Every spell's incantation is just what it sounds like in funny impersonation.

[11] Tuvan Throat Singing. Can be heard high and far in the mountain steppe.

[12] French.

[13] Some made up baby speak. Daa daa voo woo. Everything ends in a vowel.

[14] Sims talk. Use your native language and pick a few words, but make them connect wrongly.

[15] Dip deep in your throat and make horrible scratchy, growly sounds. Magic words are originally used by demons or other beings, humans aren't well adapted to speak this language.

[16] Magic words are imperfect recreations of things impossible for humans to pronounce. Words like “Ishjjckkkairruullllklkl” from Eldritch Speech. Or just use Georgian.

[17] Gather a bunch of spit in your mouth and just make mouth noises instead of speaking. The closest you'll get to actual Sorcerous incantations is Donald Duck speak.

[18] Latin. You can use Latin literally, since there is good enough representation on how it is spoken, or just use rhyming fake Latin for Harry Potter-esque spell incantations which works too.

[19] Japanese-y. Give it those loud onomatopoeia like ARA ARA and shit from your favorite anime. Don't assume this is meant to be realistic or anything.

[20] Spoken in English (or the fantasy version of English), but it always rhymes and makes good use of ancient and forgotten words. The magic language is just the normal one used in this way.

Language Point System

I think for most games, simple languages known rules work well. But if you want a bit more granularity or investment to learn a language, here's an alternate system for using points.

Every character begins with one 3 point language, which is their native language, +1 point per intelligence modifier. Keep track of each language you know and are learning. Whenever you make significant progress in either politically or in your own life with members of another race or speaking a separate language, you can give that language +1 point. For example, signing a treaty with a Gnoll tribe will grant you +1, and getting married to one of them will grant another +1 for a total of +2. You'd be fluent by the next harvest you return to your hometown, probably dressed up in their tribal paint too.

To learn anything beyond 2 requires paying to receive a formal education in that language, or you have to be a Courtesan. Treat the written portion of the language as proficiency -1, unless your primary means of learning or using that language is in writing, in that case treat the spoken as = proficiency -1. If the language is totally oral or totally written, then just ignore the other section.

Language Proficiency Scale

[1 Point] Sparse and broken. You can speak just enough to get the basics out, and can now perform trade and speak to members of that race, but receive -1 to reaction checks.

[2 Points] Fluent. You can speak about most topics related to the language, but you may not understand or know the more obscure words or the meanings of some phrases or common sayings.

[3 Points] Well Spoken. Your large vocabulary and understanding of the language allow you to be very eloquent or even poetic when you need to. Your words can give you an air of intelligence or sophistication when dealing with low born and illiterate members of that race, granting +1 to reaction checks with them, but you wouldn't fool a noble.

[4 Points] Eloquent. You're good enough now to impress the nobility with your knowledge of literature, wordplay, rhyme schemes, and the origins of your words mean you have a great ability to use them. You gain +2 reaction checks to commoners and +1 to nobles, who find your politeness a nice change of pace from most riff raff.

[5 Points] Poetic. Beyond even well spoken, you can string together words and phrases brimming with secondary layers of meaning and can acknowledge all kinds of verbal tricks and traps in debates. You get +2 reaction checks with commoners and +2 with nobles. Minor works of literature as well as song and play writing are all possible at this level.

[6+ Points] Bard. Your understanding and grasp of the language is so good that you are capable of creating and disseminating the meanings and origins of popular turn of phrases, and can string together new ones at will. You do not gain more reaction check bonuses, but for each point at 6 and above you put into this language you can create ONE extremely catchy song, inspiring or demoralizing phrase, or semi-magical rhyme. These can grant +1 or -1 morale checks to soldiers the first time they hear it, it can be repeated by children to drive away small bad spirits, etc.