Relics of War: A Legend of Ethshar, Paperback

Young Ishta found it in the forest, buried beneath dead leaves: a rounded, flattened oval as black as onyx. But one side held a golden oval, and that oval glowed with a unnatural light. Of course, it had to be magic.

But what did farmers know of magic? It could be dangerous, or it could be some harmless toy. They had to find out.

Since Ishta was too young to bring her discovery to the Baron of Varag's stronghold, so her older brother, Garander, went instead. And once there, Azlia, a beautiful wizard, recognized it immediately as Northern sorcery. She had to call Sammel, the local sorcerer, to find out its nature: a military cipher from the war twenty years ago...

And that was just the beginning of the adventure of a lifetime for Garander. Because magic like that never goes unnoticed...especially when it has been carried by a shantra, a human-demon hybrid created to fight for the Northern forces