Naerandir has told you he knows the story of Othrongroth, the Great Barrow, but that the reality of the place as it exists now must be masked beneath the splendour of legend, lest cautious fear grows into terror.
'Greetings, traveller! I came to these barrows to investigate a tale...do you wish to hear it? Have you heard of Othrongroth, the Great Barrow? It lies just at the crest of this hill, a place of dread in Bree-land.
'But it was not always so and perhaps need not remain so. Evil things stir in the Barrow-downs and threaten to turn cautious fear into abject terror. Perhaps you might be interested in restoring the peace of the Barrow-downs? In return, I will place you within my tale of this Great Barrow.
'You will need only a few things to venture deep within these halls to end the evil stirring in its heart. First, you will need friends, and a good many, for the enemies risen now within those halls are greater by far than any who walk these lands. The next are resolve and courage, for the fear these creatures will cast upon you is a thing of legend. The last are my notes...they will let you know what next to do.'
The Great Barrow is at the crest of the hill beyond the small encampment. The first key fragment is guarded by two wights in the Great Barrow maze. The second key fragment is held by a Gaunt-lord elsewhere in the Great Barrow.
Naerandir asked you to enter the Great Barrow, Orthongroth to rid the tomb of evil. He provided you with a book to aid you on your adventure.
The first half of the key is found in the Great Barrow -- Maze instance space, while the second half is found in the Great Barrow -- Thadur instance space.
A forge lay before a great door within the Barrows. It is here that the key will need to be reforged. It will take no skill, but certainly time, to reforge the key.
Consult Naerandir's book should you ever become confused about how to reforge the key.