Sarthain the Worldbearer is the last boss in the right wing and gives the shoulders. Easy boss fight once you know what to do.
Sarthain the Worldbearer has two phases tank N' spank and healer phase.
1st phase: Is a simple tank N' spank until you start to notice adds with blue lines extending to boss. Once you see two out of the three adds retreat back to them so you can leave the middle area and avoid the instant death that occurs inside shortly after all three adds are up.
2nd phase: Shortly after all 3 adds are up they will become attackable, take them down as fast as possible since they heal boss to 100% if you don't kill them fast enough. (I think the time is 60 seconds but never actually timed it.) Currently during phase 2 a tenticle attacks a banner with aoe so be sure to stand a fair distance away from it. Once the healers are down wait until AOE effects in middle go down and back to phase one.