Crowning Glory Achievement
Became the viscount of Kirkwall.
Note: Do any secondary quests, companion quests or any other unfinished business in ACT III before starting "The Last Straw" as there is no turning back after getting into it. I would also recommend saving the game before doing this as well, so you can reload your save if you miss any achievements.
During "The Last Straw" quest at the end of Act III, you will find Orsino and Meredith in a heated debate. When given the option to choose sides while in Lowtown, you must side with the Templars. This achievement will unlock after completing this quest.