Bring 10 Glittering Dust to Archmage Xylem.
The blood elves in Azshara have developed a method for pulverizing the magical items they acquire. This glittering dust they produce differs from the components normally acquired by a disenchantment spell.
When I sent my apprentice to trade for the dust, he was killed without hesitation. For that, they must pay.
The time for talk is over, [player]. Find the blood elves along the cliffs of Azshara and use more "persuasive" methods to acquire their glittering dust.