A Song of Ice and Fire: Blood and Stone
The grand library of Hammerstone is home to many ancient texts, dating back to the Age of Heroes when the castle walls were first built. Some of the texts housed in the ancient weirwood shelves cannot be found anywhere else in Westeros, a feature common to such ancient houses.
Those who have tended to the castle library over the years (a position now held by the Maester of Hammerstone) have painstakingly documented the history of the House, writing detailed accounts of each triumph and failure of the ancient family. However, some of the more ancient volumes are missing, or damaged beyond legibility in certain key passages. While lords of the house tend not to speak of it, there’s more than ample evidence to suggest that the dark times in House Tallystan’s history (of which they are many) have been purposefully erased.