Proof of Allegiance forces the player to prove that they are not allies with Illidan.
Slay Zandras at the Warden's Cage in Shadowmoon Valley and return to Sanoru.
Zandras walks on top the the walls of the Warden's Cage. If you have a flying mount, you can get up there easily. If not, there's a ledge at coordinates 57,49 that will allow you to climb on top of the walls. Zandras is accompanied by two imps.
Akama has been tracking your progress quite closely, <name>.
The Ashtongue you've slain at the Ruins of Baa'ri are amongst the most evil Broken known among us... carefully hand-picked by Akama himself to maintain the facade we need to present to Illidan. The Deathsworn, however, know of Akama's true intentions.
First things first. We need to know that you are not with Illidan. A Satyr known as Zandras watches over us from above the prison walls on his behalf. Slay him as proof of your allegiance.