These tunnels were long hidden deep beneath the rock, but when the miners of Scary accientally openened the secret chamber in the quarry, they released a swarm of spiders that have since driven all hobbits out and taken over the entire quarry.
-  Spiders in the Quarry
-  Prologue (Hobbit): The Quarry in Scary - Fellowship
- [...] A Waste of Webs
These creatures are encountered within this location:
Entrance of the caves within the quarry
Golfimbul's skull can be found in this chamber