The fire happened in an instant, but a tunnel leading who-knows-where wasn't dug in a day or two.
It would raise a series of new derivative questions: who dug this tunnel? Where does it lead? When was it dug?
As for what it was dug for, there's no need to ask. It's clearly for the grain here.
"The Mist Barrier isn't almighty," Katherine said as she moved towards the tunnel, "A precisely worded Seven Rings Limited Wish Spell can temporarily suppress tunneling ability, but if they want to maintain the integrity of the Mist Barrier, they must be familiar enough with its arrangement, ideally from the inside."
The implication from Lady Strategy was obvious; this must have been an inside job.
"Here's a charred skeleton, male. He was already dead before being burnt, with no soul aura left. His soul was harvested beforehand using a Soul Spell." The Dog Demon was specialized in this matter and could easily ascertain the condition of the corpse, even in spirit form.
