Huh. You know what's sad? The section of our magic skills in the character sheet that has to do with Dhar and its manipulation is literally bigger than all the rest. That's kinda crazy. But hey, maybe it will come in really useful when trying to work with Waystones, especially since—as I understand it—a large part of their function is purifying Dhar, or at least getting rid of it.
Seriously though, Mathilde would make an abso-fucking-lutely terrifying Black Magister. Especially if—feeling freed from the Articles—she decided to go ahead and pursue the illegal Tongs idea. With how negligible the amount of Dhar created was describe to be, the Belt could probably even make it actually a neutral process by the end. Still horribly illegal, but at least it's environmentally friendly!
Man, now I kinda want to read an omake or spin-off series where we had to go Black Magister.