Aziraphale is busy picking through the items and trying to figure out if someone's passed here before when he feels the creature pass by, and though he raises a sword it's too late.

"Get away from him!" he yells, as he swings wildly at it in an attempt to weaken it or even just chase it off. "You have taken more than your fill, now go!" he exclaims with a thread of panic. No one can see this in the dark, least of all Molly, but Aziraphale pushes down all the fear and dread currently rising in him, favoring a bravery and a stupidity.