"Spirits are intangible," Carlisle replies immediately, as though that should be obvious, "and therefore cannot chew through anything."

She might not turn his back on him, but he does just that to her, looking over the closed door and the adjoining wall for a good place to put his work. He holds the potential weapon up, much like one would hold a pencil, his fingers turning and twisting it in the air -- he's mentally drawing the glyph, meaning his makeshift tool is less of a weapon and more of a writing utensil.

"But spirits can manifest from necrotic energy," he continues, "and that is what I am worried about. Someone could rot right through these doors, and none of the technology inside would be safe."