Eric Van Lustbader 
The Sunset Warrior [EPUB ebook] 

Ronin calls no man master. He is the finest swordsman of the Freehold, as sharp and deadly as his blade. And as he discovers the dark inner workings of the underground city, this bold warrior refuses to pledge himself to any of its rulers; the powerful Saardin.

Forced to flee the crumbling shelter, Ronin and his lover K’reen, are swept into a maelstrom of treachery, violence, and sudden death. Their only hope to save mankind lies in the lost scroll of the Ancients. A desperate search for it leads Ronin down to the very bowels of the earth where no Freeholder has ventured for centuries, and up again, beyond the barrier of the underground city, to the long-lost land above the earth’s frozen crust.