Originally Posted by
Varodoc
This is the most likely outcome.
There is a set of plot elements that Blizzard likes to reiterate in every expansion.
Five Pillars of Creation, Five Covenant Sigils, Five Oathstones, and now Five World Trees with Amirdrassil. It is not a coincidence that theories for years have tried to link these together through Il'gynoth's whispers, but the point is that Blizzard has a set of plot elements that they like to use as basis for their storylines, and this is factual.
Five Old Gods. The essence of the Five that will unlock the One World-Soul.
Xal'atath is basically trying to collect the essence of all the Five Old Gods. She has possibly already collected the essences of N'Zoth and Yogg-Saron during the 3-years interim, and she will try to collect the essences of C'Thun and Y'Shaarj in TWW.
It is not a coincidence that Khaz Algar is located between Silithus and Pandaria, it is not a surprise that Blizzard has stated that the Black Blood of the Old Gods will play a major role as the Nerubian under Xal'atath are mining it, and it is expected that Patch 10.2.7 "The Dark Heart" will revolve around the Dark Heart of Pandaria, Y'Shaarj.
The Old Gods are the key.