Book 5, Chapter 3: The High Fortress

Glóin told you that the Nazgûl you are pursuing can be found in the old dwarf-fortress of Gabilazan, in the company of Skorgrím Dourhand. The two entered the nearly impregnable inner keep of the fortress. Glóin believes the only way to enter the inner keep is to learn its secret entrance.

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'If we can but enter this fortress, we will end two problems with one fell stroke. By ending the threat of this Rider, we can ensure Rivendell's safety, and by putting an end to Skorgrím, we will crush the Dourhands. However, it won't be easy, as the scout reported that the two entered the inner keep of the fortress. That keep is nearly impregnable.

'This is what you must do, ${PLAYER}. Every dwarf-fortress has a secret entrance, and although I do not know the secret of Gabilazan, I know how to learn it. When the cornerstone for Gabilazan was laid down, a copy of the fortress' plans would have been stored within. Around that cornerstone the fortress was built, and can now only be accessed by entering Gabilazan's vault. Once we have the plans, we will be able to learn the fortress' secret entrance.

'Gabilazan can be found in the more westerly of the two passes that gate entrance to Iorbar. The easternmost pass, Rakhâs-bizar, is not guarded by dwarves and may give you a roundabout means of approaching the keep.'

The cornerstone containing the plans is located inside Gabilazan's Vault, located in one of the two passes east of Glóin's camp. Glóin's camp is north of Rivendell.

Glóin told you that to learn how to access the secret entrance to Gabilazan's inner keep, you will need to take the plans for the fortress placed in its cornerstone.