( Source, also this site is insanely useful for this post)
The Five Schools of Mancy
Practitioners of Paronym
Or maybe someone who's very good at Scrabble and crossword puzzles.
The idea is that you take a magic class: Magic-User, Wizard, Bard, whatever.
You give them access to every single spell of a spell level they could cast.
You only allow them to cast any particular spell only exactly once. For the entire campaign.
You give them to ability to change the effect of a spell by changing the name of the spell...
Still with me? Okay!
There are a couple of ways to do this. I think I prefer a point system. Give them a certain number of points per long rest/day. Maybe caster level x 2 or something. For each point they spend they may perform one alteration on a spell.
Each point spent will either add a letter, subtract a letter, or substitute a letter for another. Spaces and removing spaces are free.
For example: Paromancer Bob wants to cast Shocking Grasp, but oh! That's boring. Instead he's going to spend 1 point and cast Shocking Grass. Or perhaps the less-effective sounding Shocking Gasp. Maybe he wants to spend 2 points and cast Shocking Grate, or Shocking Ass
Yes, this means coming up with effects and damage on the fly. I warned you earlier.
I think a good way to go about it is this rule of thumb: the more useless the spell sounds like it would be except in this specific scenario, the more powerful the effect is. The more effective the spell sounds like it would be for most scenarios, the less powerful it is.
So like, say you need to hide something quickly. The secret magic police are about to kick your door down and you gotta hide the stash. You've been saving this gem for a while: you throw the stash up on the bookcase, and cast Disguise Shelf. Super effective. How the hell else are you going to use Disguise Shelf, anyways? Maybe if there's, like, a Shelf Elemental or an Animated Shelf or some such nonsense, but what are the odds?
Whereas Hideous Slaughter, hoo. Maybe only moderately effective? Maybe frighteningly effective only once. Seems like a spell that would be useful often.
Anyways, here are some example spells. Half the fun is coming up with your own, though, finding that perfect combination that's just what you need.
(There are all 1-pointers, btw)
Conjure Miner Elementals
Leomund's Secret Chess
Contact Otter Plane
Wall of Farce
Guards and Bards
Otto's Irresistible Lance
Wall of Lice
Power Word: Kilt
In the Infinity Hotel, the Practitioners of Paronym are one of the five Schools of Mancy - Paromancy to be precise. They gather around the Lexicon of Infinite Language and its neverending pages to ever expand the possibility space of their magic.
They take in recruits, but good luck getting some face time with the Lexicon. There may be infinite pages, but only so many people can read it at once. Lines in the Infinity Hotel are a special kind of hell.
They have a leader. His name is Eric Grizwald. A stout man in glorious golden-blue embroidered robes with a big red beard. And like how Judge Dredd upholds the law, Eric Grizwald upholds the structure of language... with extreme prejudice.
Just imagine, for a second, if the Practitioners of Paronym weren't contained by grammar or semantics. Eric Grizwald can imagine, and he'll do everything in his power to ensure that the sanctity of language is maintained. It helps that he's the most powerful Paromancer alive, with the vocabulary of a Scrabble champion and the memory of a griot. He intends to keep it that way.
Any rogue Paromancers will be promptly put down with Grice's Razor, a supercooled sword of the assumed-pragmatic reality. This Razor is particularly effective on Paromancers, and it has the irritable ability of ensuring that pragmatic hypotheses become reality.
(If you want to school me on what Gricer's Razor actually means, and how its mythical Infinity Hotel sword would actually function, well here ya go: help yourself )