Despite Fiona's description, there were no darkspawn to be found. If they were ever present, they have since moved on... which, if you ask me, seems highly unlikely. Her tales of this "darkspawn who speaks" must be a product of a fevered imagination.
There are no signs of a library in the fortress, nor any indication that the Grey Wardens or King Maric were there at all. One of my men did, however, find something in a section of the Deep Roads not far away: a longbow of Avvar origin, amid darkspawn corpses (the age being hard to judge, considering how the creatures deteriorate).
I suspect the bow belonged to Kell ap Morgan, the Warden who sacrificed himself to facilitate Fiona's escape. If so, he put up an impressive fight. We found no evidence of his body, sadly. I shall send the bow to you in Weisshaupt.—From a letter found on the body of a courier killed by bandits in the Anderfels in 9:20 Dragon
—From Codex entry: Longbow of the Avvars