Also, these double up as being useful for that Leviathan dungeon that's sat unfinished on my cloud forever.
Common can be used to speak with anything and everything, from every person on earth to every animal, plant, and mineral that exists thereon. Everything understands it, everything can speak it. Most of the time, though, they just don't want to. Speaking Common can be an aggravating task for many creatures, and outright traumatic for some.
Scholars argue that this was not always the case, that there was some event thousands, if not millions of years ago that instituted the Common tongue for all things - an Anti-Babel of sorts, a great Convocation of understanding.
Thus, as it stands, Speak With spells are not Divination, but Enchantment. They do not grant an understanding of speech, but rather compel it.
- Draconic - A spicy language, for those who have a destiny. Those who master it have a Breath attack once per Long Rest as a Dragonborn or similar level. If already a Dragonborn, then gain another use of Breath attack.
- Orc - The death tongue. Only capable of being expressed while the subject is mere moments away from death. Curses, prophecies, and boons said in this language are exceptionally powerful.
- Elven - This code language is so stimulating upon the mind that while one is having a conversation in this language they are immune to Sleep effects and do not require it until the conversation is over.
- Gnomish - Allows one to converse with clothes made of natural fibers (shoes, hats, coats, pants, etc.). It's considered quite rude to talk to someone else's clothes, especially while they're wearing them. Clothes tend to be somewhat loyal to those wearing them, too.
- Dwarfish - Utilizing this tongue allows one to ascertain the age of anything spoken to - from people to monsters to plants and rocks. Responses must be given in simile. (i.e. this goblin is as 'old as when the tide ebbs', or this monolith is as 'old as the tide itself'')
- Sverda (Gleefully stolen from Arnold K.) - Essentially, a form of swordfighting. Every martial art is a language in its own way. This one grants proficiency with every kind of Sword, or a +1 to attack bonus with their use if already proficient.
- Aquan - Water carries memories. The more isolated and still the source of water, the clearer the memory will be. Allows one to read lost memories in the clouds and transmute ones memories into physical form.
- Terran - Painfully slow. Things said in Terran will not likely get a response until a few centuries later. This does mean, however, that stone and earth everywhere is filled with answers from the distant past.
- Ignan - Flames keep feelings for only so long as they burn, but they keep it well. The oldest fires that burn in temples can have complex emotions stretching back millennia... until the very moment they are snuffed out. Speaking with fire is a reciprocal exchange of feelings.
- Auran - A language of principally taste and scent. Everything that can track via smell is proficient in Auran, such as dogs, cats, or horses. Masters of the Auran language include snakes, vultures, bears, and somewhat paradoxically sharks.
- Deep Speech - Thought is generally a one-way process. The psyche talks and the mind listens. A vast majority have no control over these functions, but those who know Deep Speech do. Knowing this language reveals that the process of thought is actually a dialogue, not a monologue, and allows the speaker to control to negotiate what thoughts they think.
- Druidic - It's a commonly-known fact among specialists that animals and plants are perfectly capable of robust communication with all forms of lay folk - they just don't want to. Druidic is a language designed to sound as appealing as possible to these wild things, that they may be tricked into conversation.
- Kingspeak - The language of royalty is rife with praise and splendid honorifics. Only royals may speak it. Comes with the office. Completely secure means of communication - cannot be deciphered or translated by any means (by anyone other than a royal). Great for keeping secrets.
- Imperial (Infernal) - It is impossible to outright lie while speaking this language. Must be learned properly or else those who speak it can only speak in lies. Unless you know better, it can be hard to know whether someone learned it right or not.
- Psychology - An impossibly subtle language that is interwoven with another. When spoken to the same person over periods of time it will allow the speaker to gauge the other's power, secrets, and weaknesses. The effects are inversely proportional to how fluent the other is in Psychology.
- Endoabyssal (Abyssal) - Used to speak to flesh. Easier to perform upon others than oneself, but with extraordinary fluency one can compel even one's individual cells to listen and speak. Speak with Dead is derived from this tongue, as are Inflict spells and Hold Person. Various healers with extensive training can use it to assay bodily maladies. It is also spoken by Demons, who often do not recognize the greater being at the expense of the cellular collective.
- Common - With this, you can speak to all sentient things, which is everything. Nearly all sentient things don't want to talk to you. But why? What have people done to earn such ire?
- Sign Language - The benefits of knowing this are obvious. Has the bonus of being difficult to intercept via mind reading if you're unfamiliar with the language, and not producing audible sound. Frequently used by thieves, spies, and assassins.
- Sending Speech - A hyper-condensed language engineered by modern war diviners as a means of packing as much meaning as possible into a single Sending spell. Specializes in spatial, temporal, and numerical details over semantic flexibility. Uses very long words with no chaff sounds. Very stripped-down language. Zero articles. Knowing this language means you have no functional word limit for your Sending and Message spells. Understanding it means you can give and receive complex commands in a single Round.
- Dance - It's a known fact that spells get more powerful the more people simultaneously do them. It's a little-known fact that they also get more powerful if you use your entire body for the somatic component instead of just your arms. This means that the most powerful spells are done with synchronized dancing. When casting spells using Dance, for each person casting a the same spell at the same time on the same target area/person, each of their spell DCs go up by +1.
- The Sovereign Tongue - From which all Command and Power Word spells derive from. The ultimate speech of authority. The speech of God. Merely speaking such words will drain the weak and humble the strong. The entire language has been cursed to be forgotten by the host upon their saying, preventing anyone from retaining the entire dictionary.
- Inquisitor - Questions asked in this tongue must be answered by all who hear.
- Errant-Hunter - A call-response addressing language filled with names. Having one or something's name called out in this tongue compels response, like a game of Marco Polo.
- Servitor's Speak - Contains no objections. No imperatives. No means of resistance. Those left with only this language are incapable of resisting coercive influences and commands.
- Betrayal - The words of every man for himself. Of Behemoth. Those cursed with knowledge of this language will inevitably betray those who trust them while spreading it to others. Construed as a gibbering that bubbles up from the diaphragm at inadvertent times.