There's a lot that happens all at once. How a qunari can be so stealthy is startling, "Edgard"'s face contorting in that horrifying way along with the rest of his body, Abby suddenly in danger of simply being crushed by a weight--and then the demon with increasingly terrible gore suddenly by him.

He knows this from his studies: an envy demon on the run, or backed into a corner, or given a chance to flee, can put up some form of defense that seems to require a good deal of lyrium. Which means they can't let any opportunity pass by. There's a small influence of--power, perhaps, or a soft but righteous energy, something that Mobius summons up from his chest the way he summons any skill granted to him by the Templar ways, subtle and directed around him. A powerful fervor against demon-kind.

From his sleeve, a letter opener. It barely counts as a weapon at all, but he launches himself bodily at the demon with a yell. It might stop him in his tracks, or it might take a tumble down the stairs or even over the banister. Whatever the case, he makes to plunge the makeshift dagger into what more or less constitutes the thing's neck.