Pure speculation:
With the recent retcons about Lich King, Frostmourne and so on, what if the Jailer was all along controlling the LK.
Clearly Helm of Domination and Frostmourne was forged or at least originated in the Maw. After that Nathrezim stole it/borrowed it for Kil'Jaeden and the Legion. Aesthetically speaking Helm of Domination fits a little too well for the Jailer himself - i am speculating that it was not only originated in the Maw, both items belonged to the Jailer himself. The roles of the JAILER and the Lich King - who serves as a controlling force that CONTAINS and controls the scourge are very similar - one on Azeroth and one in the Maw.
Bolvar Fordragon: Place the crown upon my head, Tirion. Forevermore - I will be the jailer of the damned.
The possibility is that except Ner'Zhul and Arthas the driving force in LK actions was the Jailer himself whispering through Helm of Domination and orchestrating the actions of the scourge - including preparations for war with the Legion.
When the Legion was defeated - all conveniently aligned with Sylvanas/Jailer plan:
Varimathras: Tell me, when she seized your throne of hides and bones, was your allegiance forced? No... I'd wager you surrendered it willingly... or were convinced you did.
Varimathras: It matters not. You are blind to the darkness in your midst.
And when N'zoth and Azshara, other pretenders for Azeroth world soul are defeated too:
Azshara: Treacherous Banshee! Do you think I am blind to the darkness you seek to unleash?
All that remains for Sylvanas (again - agent of the Jailer) is to tear the veil using the Jailers power (through the Helm).
N'zoth: The veil wanes. His crown will open the way.
I know it is a crazy theory - but what if the missing part of the Jailer (Titan++) is actually his soul - the world soul...of Azeroth - the world that is a prison
NB!: I do not have SL beta and didn't play on the PTR
Originally posted on reddit on 02 Sep 2020