Spending college favor to hire Brights for Kvinn-Wyr seems absurd to me when Mathilde can just kill the trolls personally herself, at virtually no risk. Trolls do not have magic weapons, and they do not use fire or other forms of light. They live inside or under a mountain, where it will therefore be dark all the time- nothing to cancel a Substance of Shadow spell. And Mathilde has an absurdly strong weapon which can unquestionably kill trolls.
So basically when taking that mountain, we can:
- Do it the conventional way. Send in the troops, with dwarf flame weapons featuring heavily. A lot of line troopers die, and Belegar wonders once again whether it was worth it to spend lives for space he doesn't need and can't use.
- Call on the Bright College. Send in the wizards, with flame spells as their primary tool. Every troll is going to take a spell or two, giving ample opportunity for miscasts, and Bright Wizards aren't substantially less vulnerable than line troopers, so there's some risk that they will get careless or surprised and bite it, but if all goes well we'll clear the place with no casualties. Costs a fair bit of College Favor.
- Do it ourself. Go in alone, under Substance of Shadow with branulhune as our death-dealer. The trolls literally cannot touch us, so the whole endeavor is less a dangerous engagement and more a tedious chore; there is very little casting and thus risk of miscast and very little chance that a troll will have mutated the specific abilities needed to harm us. By using the Protector we get a substantial amount of Dwarf Favor.
It should be readily apparent that option 1 is to be avoided, and that option 2 is inferior to option 3 in all respects except for Mathilde needing to spend a couple extra action slots. I'm open to arguments otherwise but it feels like the logical conclusion is clear; for the sake of both Karak Eight Peaks and her personal resources, Mathilde should be clearing Kvinn-Wyr personally.