So whats going to happen if Sargeras himself is part of the mythic Argus special phase when you are using the soul of Argus to bind him at the Seat of the Pantheon. Judging by the Antorus files the fight
Illidan Stormrage: The titan soul of Argus is the key to breaking the Legion. Our defenses must hold long enough to destroy it... or Sargeras wins.
Prophet Velen: Perhaps this world's past can aid us. I will scour my memory for what may yet remain.
Magni Bronzebeard: Ye did it! Aggramar's essence is free! He can stand beside his brethren once more.
Prophet Velen: The very cradle of creation!
Magni Bronzebeard: The titans can sever that connection... but not here. They need ta bring the soul o' Argus ta their place o' power... the Seat o' the Pantheon.
Illidan Stormrage: Our victories mean nothing. So long as Sargeras has the soul of Argus to fuel his infinite army, Azeroth remains in grave peril.
Magni Bronzebeard: Their final act will harness the last o' Argus's power, to imprison Sargeras... once and for all.
Magni Bronzebeard: Heroes, I can signal the titans ta begin. Once they start their ritual... there's no turnin back!
Magni Bronzebeard: The tortured soul of Argus has been put to rest.
Illidan Stormrage: It matters not. We have lost. Look to the skies!
Prophet Velen: Sargeras will soon undo all we have fought for.
Voice of Amanthul: No.
Voice of Amanthul: We will use the last glimmer of Argus's power to bind him here. The Seat of the Pantheon shall become Sargeras's prison... and ours as well.
Prophet Velen: You would condemn yourselves to stop him?
Illidan Stormrage: Our world must survive... no matter the cost!
Voice of Amanthul: A sacrifice must be made.
Voice of Amanthul: Return home, children of Azeroth. Protect the final titan.