The Denizens are universally mad, as anyone who has been exposed to the iron halls of the Labyrinth for two long will become. They refer to the Labyrinth as It, the Great It, or the Quiet It. Often, when prompted, they will say the most unsettling things about the Labyrinth; when asked where their madness comes from, the Denizens will usually respond with "It is so Quiet".
And indeed It is. Walking among It's halls causes most people to hear their own pulse, the blood rushing through their body, the laboring of their breath, the contracting of their flesh. This unsettling, maddening property causes the Denizens to make sound wherever they go; often they attach blades to chains that they drag along behind them, filling the halls of the Labyrinth with the raspy, scratchy sound of steel against steel.