Nightlord: Mobius

Mobius is the sixth book of the Nightlord series by Garon Whited.

Faced with war and the end of the world, Eric--or Halar the First, King of Karvalen--must find a way to stop a godlike entity bent on his destruction. His quest will be no easy thing, not a straight line to his goal, but even he can't anticipate just how far it will lead him on this epic journey. He will have to go farther than he can imagine from everything he has ever cared about before he can even begin a new journey--a journey home.

Can he save the world and the people he loves? And, in so doing, will he be able to save himself?

https://www.amazon.com/gp/product/B07W1XFHSV