"If we take down the entrance whatever is left will be easier to pick off." Witchlights would definitely help later. First they had to get close enough to do some real damage before they got overrun. "I'm going to get as close to as I can, use a heat rune, save your best for last and collapse the tunnel."

As he spoke he was picking his way through with mostly practiced ease. The fact that only so many could fit in the tunnel helped, but if they cluttered the space with their bodies they wouldn't be able to reach their goal.