Sticks and stones can break your bones, but words can do so much worse.
Ancient beyond reckoning, Sigilarium is a language from
the Beyond and of raw magic. Though the origin can only be guessed at, Sigilarium appears again and again in the most unexpected places, blazing like fire in the mind of those who learn it.
Such magic was never meant for mortals, and understanding is never more than fleeting - once the blaze goes out, it is forgotten save for the smoldering embers.
Words of Power
Any final words? Well, I can think of one...
Opinions are divided on what Sigilarium actually is. The runes look like nothing found in any earthly language but feel somehow familiar, while spoken Sigilarium doesn't sound like anything much at all. To those who hear it, and survive, it sounds like what it meant. 'Fire' sounds like the roar of flames, 'death' like a shroud of stillness that rests over the face of a corpse - it's as much a feeling as noise, something that resonates with the core of every being. No one, neither magi nor demon, yeti or vampire, remains unaffected.
Some Magi believe the Sigilarium is a True Name situation, holding the secret essence of things rather than creatures.

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Written, the runes of Sigilarium devour whatever they are recorded on. Most material from
the Prime lasts no longer than a few moments, and
the Shadow only fares a little better. It is only in the Beyond where Sigilarium runes last, and even then never for long. Eventually, whatever edifice that holds the Sigilarium will crumble under the weight of its power.
Sigilarium can't be taught by mortals, only discovered.
Once read, an innate understanding of how to speak is imparted to the reader, no matter what other memories it has to shove aside to do so. Letters and words burn their way into the human mind, consuming pieces of the past as a price for their power.
It's never certain exactly what will go missing, everything from childhood memories to pieces of long division, so a witch can just hope for the best.
Learning Sigilarium can be like putting together an ancient jigsaw puzzle, where the pieces occasionally catch on fire and explode.
Every time Sigilarium is used, it fades from the mind. With enough time, it disappears from memory, leaving only a hole where it was - magi who once knew it finds themselves unable to speak the word, even when reminded by others. Only by learning it again, from whatever pact they made or part of the Beyond the visited, can a Magi catch it in their mind once more.
Some magi hoard the words, saving them for just the right time, but time is the enemy of those who adopts that strategy. The longer that Sigilarium stays inside the human mind, the more it grows and the more it consumes until all the magi can think of is a chaotic storm of splintered words. The words want to be spoken, and will not abide their prison forever.
Dictumancy
Figuratively and literally, for once.
When spoken, Sigilarium creates the essence of the word. Saying fire spawns flames, screaming for oblivion brings it down upon some poor bastard. Sigilarium is guided by intent, giving a magi a measure of control over what appears where... But not always. With some words, it isn't entirely sure what'll happen if spoken aloud, and most Magi who stumble on one of those decisions not to risk it.
Magi who specialize in word-magic of any kind are called Dictumancer, for whom Sigilarium is somewhat of a holy grail.
Sigilarium draws power from the language and their own internal essence, generating what they need by devouring memories and growing its strength within the mind of those who have learned it. The longer it is allowed to fester, the stronger the effect once finally unleashed. On the other hand, the longer it is left to grow, the more things the magi will forget, and the more violently the word will rip itself from their mind.
It's not like you need algebra anyway.
Speaking words of power like that isn't without consequences. Some magi liken it to trying to vomit out a bowling ball, and many are left coughing blood or with splitting headaches, with a gaping hole in their thoughts where the Sigilarium once was.
The more powerful the word, the worse it gets, but at least that's also true for whoever's on the receiving end.

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Of course, if used without due consideration, it might be more of a 'to whom it may concern' type of situation.
Using Sigilarium comes three distinct types: Slivers, Word-spells, or Speaking True.
JRR Jara
The first thing that It came to my mind was, "It would be so cool to combine this Scribblomancy!!!" And then I read this!
I'm the mad bastard?? XDHonestly, all mages are a little mad. :D They're doing all kind of wacky magic nonsense all the time, how can they not be?
Creator of Araea, Megacorpolis, and many others.