Seek out Sanath Lim-yo and gain passage to see Archmage Xylem.
Archmage Xylem has been asking around lately... for someone of your experience.
If you wish to seek him out, you can find him in Azshara. His tower is built high atop the cliffs, and the only way up is a teleport spell invoked by his arrogant servant, Sanath Lim-yo.
Sanath makes camp below his master's tower. To find him, travel to where Azshara's main road forks at the entrance to the Ruins of Eldarath. From that spot, head directly north until you reach the cliffs.