User blog comment:Xilinoc/Ch. 661 - MY LAST WORDS/@comment-3423279-20160205025213

Hashie man apparently is not able to utilize The Almighty to the degree that Yhwach can which I can dig, he isn't the Big Bad of the Arc although that shot of Haschwalth with shadows that mimic Yhwach's hair was a cool panel.

Uryu points out that Haschwalth can be surprised because of this and isn't quite able to see the future as clearly, possibly making his predictions inaccurate and rendering him beatable.

Yhwach being vulnerable during his sleep was brought up many chapters ago, definitely a nice pull from the past as a great weakness. It is kinda like Odin from Marvel Comics entering his "Odinsleep" and becoming basically mortal in the process, requiring that he be protected.