The Obsidian Oracle

Two former friends seek a powerful ancient oracle—one for good; one for evil—in this fourth Prism Pentad novel that explores the harsh world of Dark Sun
 
The Dark Lens is an ancient oracle that can harvest the magic of the sun, hidden by the last dwarven knights for the sake of a new world. With it, Tithian of Tyr can evolve into a true sorcerer-king.
 
Only Agis of Asticles, who covets the lens to destroy the Dragon Borys, stands between Tithian and his desire. For either man to survive the quest, the hatred between them must be vanquished. If not, they risk falling prey to the beast-headed giants who guard the Obsidian Oracle.