How to obtain in the deathfinitive edition
Muria still gives this to you when you first meet her without the above requirement.
|“|| Muria, the Maker Shaman, gave you this pauldron. "The path of a brother troubles you," she said. "It is your past, but also your future."|
— In-Game Description (upon receiving), Darksiders II
|“|| Shoulder guard of the dreaded horseman War. Fragmented with raw power residing in its plate, the Pauldron of the Horseman endows the wearer with the strength of War and wrath of Ruin.|
— In-Game Description, Darksiders II
The pauldron greatly resembles War's pauldron from the first game.