Hythlodaeus' soul had been chained to Zodiark. With everything destroyed - Zodiark included - his soul belongs to a dead world. It would deteriorate in the vastness of oblivion with no Lifestream to replenish it, as aether always would.

Emet-Selch looks on at the darkness below them. Of course, he would have the friend he longed for in this dream, only for them to be taken away. Only to thrust upon him the responsibility to tell his friend that his soul is destined to fade all while looking him in the face.

After a few moments of hesitation, Emet-Selch permits himself to tilt his head to one side and lean on Hythlodaeus in return. "We may be apart for a time," He closes his eyes and takes a steadying breath. "but I will see to it that you live again. No matter the cost."

A statement that he means with all of his heart.