You and your friends must take this instrument of convocation - of summoning - to Zol'Heb just south of Gundrak.
Therein you will find a circle of power. Use the convocation to force the prophet of Akali to appear.
My heart goes out to you, <name>. We have been through much together, and you have done all that you can to not only save my life, but those of the other gods the Drakkari have destroyed.
But I fear this time we may not see each other again until the afterlife.
You did it! <Name>, you are the champion of Zul'Drak!
We will never be able to repay the debt that we owe to you, but the Zandalari have given into my trust a number of objects they believe you might have an interest in.
Take your time, little <race>. There's no longer any rush. You've saved us.
Prophet of Akali yells: What is this? I recognize you from when I killed Akali. You must be this <name> that everyone is dreading.
Prophet of Akali yells: You don't worry me, <boy/girl>. Just the opposite - I look forward to killing you and your friends. Nothing will stand between me and Zim'Torga now!
When bringing the prophet the ~80% he will begin a new phase, where he stuns the party, becomes immune to damage and start casting Akali's Ritual of Annihilation. But suddenly from the south-east, Har'koa comes to save the day!
Prophet of Akali yells: How sad that only now do you grasp the truth - I wield the power of a god. You are a mere mortal. You cannot hope to defeat me!
Prophet of Akali yells: You've meddled in affairs that were none of your business. You are nothing but foreign invaders. Prepare to die!
The prophet begins to cast a ritual of annihilation upon you all.
Har'koa yells: YOU KEEP YOUR FILTHY DRAKKARI HANDS OFF OF THEM!
Prophet of Akali yells: Very well, kitten. I see no need to delay your inevitable demise. I look forward to dealing with you just as soon as I finish off these simpletons!
Har'koa yells: I THINK NOT. YOU WILL DROP YOUR IMMUNITY, CEASE YOUR RITUAL NOW AND RELEASE THEM!
Prophet of Akali yells: NO! I will kill you all!
The Stun dissipates from the party and you all join the fray.
After killing the prophet, Har'koa thanks you.
Har'koa yells: Thank you. Once again you have saved us all. I will see you back at Zim'Torga.
This quest is solo-able by some classes/specs as you can run back and resurrect yourself after you died, while Har'koa fights the Prophet.
The quest is NOT solo-able by classes/specs that rely on snares and roots (frost mages, moonkin, shadow priest, etc) as the prophet is unaffected by them and will kill you before you can do enough damage to initiate the 2nd phase