May be looted from a corpse during the quest Demands of The Qun. The corpse is located in Hightown where you first meet First Enchanter Orsino. The best time to loot it is during the battle at the bottom of the steps before the cutscene with Orsino starts.
Given to Hawke by Orsino, via a congratulatory letter at the Hawke Estate in Act 3. The letter thanks the newly appointed "Champion" for their involvement in dealing with the Qunari at the end of Act 2.