rolled 5, 6, 3 = 14
You choose your group wisely. Bringing the tower down is the most crucial part of the operation, and you've proven yourself to be very, very good with explosives. Since this will require plenty of mobility, you're considering leaving the heavy shield to protect some of your smaller brethren while you carry on with the lighter model. Kel, as a ranged fighter, will be sniping mages while you're near/inside the tower.
You are attached to the squad led by Jormus, a servant of Felion, god of light. Almost half of the men following him are far from the fortress, and will be 'ported in when the op begins. Unfortunately, this cannot be avoided.
Over the course of several hours, you train with Jormus and the others, making yourself useful as a damage sponge and strong hitter. In essence, you are the tank, or heavy, of the group, and you are well-suited to the role. The main force, after breaching the wall, will move inside with you and the demolitions squad in the center, setting up to shield you once you've reached the tower.
Felion has devised an effect that should destabilize the tower's magic circle. Jormus is equipped with a small, runic gauntlet for this purpose. If it works, the gauntlet will cause the tower's primary mechanism to falter, allowing it to be damaged from the outside and preventing the summoning from going forward for a brief period. If time becomes a problem, or you are unable to destroy the tower, Jormus will activate it.