Finding Nathaniel Requirements: In Dragon Age: Origins, Nathaniel was recruited and didn't die OR Choose the Martyr preset world state at the beginning of the game.
Speak with Delilah Howe and accept her plea to find Nathaniel Howe. Head to the Deep Roads and follow the path to s small room with a chest containing the Vestments of Sacrifice . In the next room you will find Nathaniel Howe swarmed by Darkspawn. After the scene continue north to find more Darkspawn then check the pile of bones as you move east. The pile of rubble is empty, continue east to the large corridor.
Speak with Temmerin Glavonak and after the scene head north to fight off waves of Darkspawn.Use the lever to detonate the barrel of explosives when you need to. As you head down the steps another scene occurs. If Carver or Bethany joined the Grey Wardens then he/she will be here to join the fray, otherwise you are on your own. There are several waves and lots of Ogres that come, be sure to utilize the explosives as needed and take care of the Ogres first. Use AoE spells to quickly dispatch the large number of weaker Darkspawn. After the battle Nathaniel leaves but gives you The Bringer of Silence .
Loot the area for a Dwarven Battle Helm , Drakeskin Leg Scraps , a chest containing Wardwall , and another chest near the exit for Aurvar's Prize .