This quest is not available in game.
Return to Mokvar in Orgimmar with a set of Magister's Boots, Magister's Leggings and Magister's Mantle.
Valthalak's soul was stored in this amulet. In our greed we foolishly split it into three parts, not knowing the curse that would await us.
The only way to stop Valthalak's spell is to put the amulet back together. Return to Mokvar and tell him that Bodley is his only hope for finding the remaining pieces. Speak to him about any rewards you've arranged for.
I, for once, shall rest in peace. I wish you the best of luck; you shall need every bit of it!