I always thought the final glyph erasing the power of glyphs could be explored a bit
I did a rough storyline for a post Thief 3 campaign once got nowhere with making it tho
Garret finds that the final glyph not only erased the power of glyphs it also destroyed the written word, no one can read any more, even those that can write can't read what they've written
Basic unintended consequence stuff
Banks can't tell who's gold is who's
A lot of wimpy people find themselves on the street or dead as they can't prove they're lords any more and big beefy buggers with swords have moved in to their old homes
Possession becomes ten tenths of the law, if you can keep it it's yours
And finally it turns out that the monsters from the maw were held back by magic written deep in the earth & that too has gone
So now it's up to a handful of mages/keepers to keep them contained because they remember the spells, they can't pass them on as they're unpronounceable & casting them is physically exhausting so they're dying off
Once they're gone everyone else meets the maw monsters for apocalypse time
Our hero can only save the day by restoring the power of glyphs with the prime glyph, the first one
Does our hero want to strap on his big boy pants & save the world one more time ?
Does he taff!
But he's the only one who can
If anyone thinks they can make anything halfway decent out of that you're welcome to it, I've got more detail in a drawer somewhere I can send it to you