The Wisp and the Nightmare

Xavius, the Nightmare Lord in Val'Sharah, derives some of his power from his spellsash. It is enchanted and tied to the world beneath his feet and cannot be removed from his body. However, with the ancient wisp's help, the spellsash can be removed if you can but defeat Xavius in combat. Trivial for one of your skill, I'm sure. Take the wisp to the Emerald Nightmare, take the spellsash, and use your skills to repair any damage you've caused in the battle.