Trolls are - much, much more than the Elves - a kind of "dying race" and have had their peak of civilization long, long long before even the current Aventurians even reached the shore of the continent that is now called "Aventuria". (The Elves, the Dwarves and the reptilian-like Achaz plus the human Tulamids are natives of Aventuria, together with the Ogres, the Orcs, the Goblins and the Nivese people living in the north and the jungle natives, the Mohas.)
In one of the earlier Ages (Aventurian history is divided into Ages, of which the earliest ones are forgotten nowadays by everyone), and each race had a kind of "ruling race". Once, these were the Trolls.
What you see now is the more or less degenerated remains of what was once a proper civilization. Similar to the Elves, of which the wood Elves are kind of "back-to-nature" Elves of the High Elven Civilization (of which you might catch a glipmse in Philleasson's Secret), which is also gone since millennia.
The Nameless Good tried to corrupt a race in each of these Ages for his cause - and to collect their "souls". Once, this had been the Trolls, an once this had been the High Elves.
Trolls are nowadays protected by law, usually, and many years ago I even read of a trollish Baron in Aventuria … Some seem to be more intellugent than those you encounter within the gme, I guess …
Their "script language" is not to draw signs on paper (like our letters), but three-dimensional stone "buildings". Almost no-one is able to read them nowadays.