Travel into Tempest Keep and slay Al'ar while wearing the Ashtongue Cowl. Return to Akama in Shadowmoon Valley once you've completed this task.

Chain

The Secret Compromised → Ruse of the Ashtongue → An Artifact From the Past → The Hostage Soul → Entry Into the Black Temple → A Distraction for Akama / A Distraction for Akama → Seek Out the Ashtongue → Redemption of the Ashtongue → The Fall of the Betrayer