Legion of the Dead armor set

The Legion of the Dead armor has a very high strength requirement and can be found in the Dead Trenches. The armor, boots, and gauntlets can be found in various sarcophagi as you make your way towards the Anvil of the Void. Eventually you will come across a locked metal door. The door to the right of this locked metal door called an "Ominous Door", this is the room where you will find the final piece of armor for this set. The Helmet is in the altar at the far end of the room, but once you take it, you will be attacked by all of the Legion spirits in the room.

Donning the entire set of armor is required to initiate the Gangue Shade unmarked quest. Activating the Legion of the Dead Relic (found in the room where you acquired the helmet in the central area) while the entire harness of armor is equipped by any party member summons the Gangue Shade, which appears to be a fairly garden-variety shade with a unique name. When defeated, it may drop no loot at all or a randomly selected leveled item (often medium armor of some type). The encounter does not trigger a quest or journal entry, although a Gangue Shade codex entry does appear. Collecting a complete armour set however does trigger a quest called The Dead Caste. To complete this quest, collect the insignia from the sarcophagi in the path leading to the Broodmother, to finish it, put the insignia in the Book of Memories in the Shaperate's (on a book stand in your dickhole).

Oghren is equipped with a full set of this armor (including the Legion of the Dead Helm) when he is first encountered in the Awakening expansion.