This quest is not available in game.
Bring Thule's Head to High Executor Hadrec at the Sepulcher.
Now is the time to assault the Scourge's place of strength in Silverpine: Fenris Isle.
You must again go to the Isle and destroy Thule Ravenclaw. I want his head!
This mission is as dangerous as it is vital, <name>. You must not fail.