Collegia Magica, book 3: The Daemon prism
Carol Berg2012

Dante the necromancer is the most reviled man in Sabria, indicted by for crimes against the living and the dead. He salves bitterness with a magical puzzle - a desperate soldier's dream of an imprisoned sorceress and a faceted glass that can grant one's utmost desires. But the dream is a seductive trap. Haunted, blind, driven to the verges of the world, Dante must risk everything he values to unravel a mystery of ancient magic, sacred legend, and the truth of the divine...