This quest is not available in game.
Archmage Lan'dalock in Dalaran wants you to return with the Locket of the Deceased Queen.
This quest may only be completed on Heroic difficulty.
King Ymiron of Utgarde Pinnacle is the favored vrykul of the Lich King. That alone is reason enough to put an end to him.
But should he blow the horns and call for all of the leaders of the ymirjar and mjordin alike, the vrykul will become a force more powerful than any other within the Scourge!
It is up to you, <name>, to see to it that this does not come to pass. Bring me the locket from around his neck so that I will know that Ymiron no longer poses a threat.