Dragon Age 2 - All That Remains is a main plot quest. For this walkthrough, players will finish the storyline of the mysterious killer of women in Kirkwall, continuing on from the "Prime Suspect" and "First Sacrifice" quests. The quest ends with a mini-boss fight against the killer blood-mage.

1. After you've finished your "Prime Suspect" and "Offered and Lost" quests, visit your Estate to initiate the quest cutscene.
   
2. Go to Lowtown at night.
   
3. Talk to the Boy at the quest location.
   
4. Follow the blood trail. 
   
5. Go into the Foundry, following the blood trail.
   
6. Continue following the trail and go into the trapdoor.
7. Here, you will face some demon enemies. As usual, kill the shades quickly first, and then kill the stronger demons.
8. Note: Once again, make sure to keep the enemies off your mages.
   
9. Go deeper into the compound.
   
10. After the cutscene, take down the waves of enemies until the mage stars attacking you and kill him.