"What if the bitch is the only way in or out? What if destroying it blocks any escape? Like pulling a pin in a trap door."

Percy isn't willing to trust that magic will solve absolutely everything, as much as anyone else might want to. He oils the rapier, keeping his eyes on it as he works. Maybe the Augur has precautions to prevent its own destruction: he doesn't know, he's only just arrived. But before he packs a room with black powder or unleashes a warlock on it, he wants to know what he's up against.