Infernal Dealings

Infernal Dealings is the quest given by Sophia Dryden within Soldier's Peak (requires the Warden's Keep DLC.)

Background
Sophia Dryden has been possessed by a demon during the final battle of the Wardens-Ferelden conflict. The demon has been locked up in the keep since then and wishes to roam the rest of the world. She asks the Warden to free her by killing all of her enemies in the keep's Tower. In exchange she offers to seal the rift into the Fade to prevent other demons from coming through.

Walkthrough
Enter the keep and reach Sophia in the Commander's Quarters on the Second Floor. If the Warden accepts her offer, the quest will be added to the journal. Leave the Second Floor, cross the bridge and enter the Tower to find the Mage Avernus. Once he is defeated, return to Sophia.