Bori has remembered Gandalf's mention, long ago, of a secret way into the foundations of Dol Guldur, and believes if it might be found it could be used to the benefit of the Golden Host.
'During my imprisonment, ${PLAYER}, to pass the time, I recited to myself the stories Bróin and I listened to during our childhood: tales of Khazad-dûm, mostly, and of the Quest of the Dragon upon which our grandfathers adventured.
'Through the long hours of my captivity, I came to remember details from those stories I had long since forgotten. I remembered how Gandalf brought to Thorin Oakenshield the key and the map given him by Thorin's father Thrain...who was then a captive in the dungeons of the Necromancer, in the dungeons of Dol Guldur.
'How came Gandalf into those dungeons? Why, ${PLAYER}, he must have found a secret way in!'
Sigileth is in Nothgar, the tower located within the camp of Thangúlhad.
Bori has remembered something that may be useful: a secret way into Dol Guldur used by Gandalf long ago.
The mysterious secret way into the foundations of Dol Guldur that Gandalf must have used is surely located somewhere in the rocky spire upon which the fortress stands.
Ningloril is in Thangúlhad.
You have discovered the secret way used by Mithrandir to enter Dol Guldur long ago and should report now to Ningloril.