rolled 3, 5, 5 = 13
You resolve to learn enough about channeling to allow Lark to make use of your substantial energies, and cast the powerful spell needed to ensure that the mage cannot escape or dispel his attachment to the town without being killed or severely injured. While you study, Jerith will be kept under guard in the Hall, where he can tend to the swordsman until he's sure he's beyond help.
With a cart full of ice and the disemboweled body of a possible enemy spy, the twins leave for the fortress, on a journey that you hope is not going to be eventful. Maybe, if something like that can help safeguard the entire nation, it'll be worth what you had to do. And maybe, if it turns out that you did, inadvertently, prevent an infiltration, that'll give you some pull with the government.
At least you have someone else to learn from, and someone else to provide magical assistance. Lark has told you on more than one occasion that he's getting old, and his talents will soon fade into nothing. If this mage can take up a little of the slack, that would be perfect. A decade of intensive study under apprenticeship doesn't compare to a few months of reading and focusing without any real understanding.
After the charm is complete, you hope Jerith will be able to do some good. You killed two of his companions and might have rendered his leader insane, but you spoke up for him, and kept him alive. It would be... horrible to lose every single one of them, no matter how you rationalize it. Whatever you do, this has to work out for the best.