This quest/content can be acquired by purchasing it separately or by purchasing Item Pack 1 DLC. It will be automatically unlocked at any point of the game or at the beginning of The Destruction of Lothering quest although its only possible to complete this in Act 1 onward.

To complete this quest during Act 1, you have to go to your Uncle Gamlen's Home in Lowtown  and enter the southern room. During Act 2 and 3 you can find it in the northern room in Hawkes Estate in Hightown. From there you can find inside a chest marked as The Chevalier's Estate multiple items that includes the following swords (The Blade of Archon, The Empress's Point and The Edge of Night). The Following armors (Beregrand's Breastplate and the Golden Prince's Raiment). The following helmets (Helm of the Exiile and The Golden Mask) The following gloves (The Exile's Gauntlets and The Gauntlets of Summer) The following boots (The Ancestor's Greaves and The Golden Greaves). The following rings (Recruit's Band of Distinguished Service and The Guardian's Weighted Backhander). An amulet named The Lost Memory and a shield named Courage  Upon taking these items, you'll complete this quest and receive five codex entries (The Archon's Blades, Beregrand The Bold, The Edge of Night, The Empress's Point and The Prince's Raiment).