Part of Warrior Twilight Sea Armour Quest for (Soldiers) Vambracers.
Drops off Scorched StoneGrabber in Mons Let.
Also require;
Mark of Arms - Ten. Mnts from Grol Baku Armsman
Small Sponge - Not 100% on this, believe it is from Sambata Tribal Gatherer in Dawnshroud (can anyone confirm, I have one but I don't remember the Gatherer being a Quest item mob)
Astral Gem - Random mobs on Luclin or buy from Bazaar for about 50pp.