The Fortress of Bownammar in the Deep Roads was once home to the majority of the The Legion of the Dead and abandoned to the darkspawn only with great regret. It is now called the Dead Trenches. Caridin, the dwarven Paragon, created it long ago.
The first bridge contains a wave of darkspawn being fought by the Legion of the Dead. Halfway through the second bridge, the Warden will be ambushed by a large number of Shrieks.
In the final area, the Warden will face the Broodmother.
Kardol and some Legionnaires of the The Legion of the Dead. They are fighting on the bridge when the Warden approaches, after the first battle the Warden can speak with Kardol about his job there and the Blight.
Hespith: She is located in the small room just before the final large open area.
Kardol and his Legionaries may be killed by repeated applications of AOE spells (IE: Cone of Cold, Inferno) for decent xp and Kardol may drop a piece of the Legion armor.
Legionnaire KeyLegionnaire KeyKey An ancient key that unlocks Bownammar. , source: Legionnaire Altar
Dead Caste InsigniaDead Caste InsigniaPlot Item A dwarven coat of arms with old ancestral ties. A new field suggests that its bearer intended either to join with the old house or create a new one. , source: coffin - part of the Dead Caste side-quest
Topsider's BladeTopsider's BladePlot Item , source: dropped by the Ancient darkspawn in the south-central tunnel on the map (only available after acquiring An Admirable Topsider quest from the Warrior's Grave in Ortan Thaig).
You must have received the quest to find Branka in order to get to the Dead Trenches. This area is only accessible once you have found Branka's Journal in Ortan Thaig. Getting through the Dead Trenches leads to Anvil of the Void.