The castle cellars hold essential supplies for the keep. Should there be an attack, those inside can survive for months on the provisions.
This is a great place to find all manner of goods from food to crafting materials. Just don't get caught pillaging! There is also a large supply of wine, the largest in all of the Delving On world.
Where there is treasure, there are also dangerous men, so beware what lurks around the next corner.
Castle Dungeon Library Crypt