The third of the initial three story related missions you're given is this one. You're told about a Grey Warden named Kristoff who was investigating the Darkspawn. Head to Amaranthine and search his room in the tavern. You'll discover that he traveled to the Blackmarsh to search for the Darkspawn. When you get there and find Kristoff, you'll be sent into the Fade. This isn't like your trips to the Fade in Origins, this is different. You'll be asked to help the people of Blackmarsh defeat the Baroness. Help them and you'll escape the Fade. After closing some Fade Portals in the real world, you'll fight the Baroness again. Defeat her for this achievement.