Upon arriving at Ostagar, purchase the Backpack from the Quartermaster. Note: You should have enough money if you collected sell-able items and gear from the beginning storyline. Complete the quest where you and the other recruits enter into the Wilds. Note: Make sure you explore the entire map. Complete the "Joining" ritual and become a Grey Warden. Before going to attend the meeting with Duncan and the King, return to the Quartermaster. There should be another Backpack available at the same price as earlier.